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⇱ CWE - CWE-59: Improper Link Resolution Before File Access ('Link Following') (4.20)

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Home > CWE List > CWE-59: Improper Link Resolution Before File Access ('Link Following') (4.20)  
CWE Glossary Definition
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CWE-59: Improper Link Resolution Before File Access ('Link Following')

Weakness ID: 59
Vulnerability Mapping: ALLOWED This CWE ID may be used to map to real-world vulnerabilities
Abstraction: Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
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Description
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
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Alternate Terms
insecure temporary file
Some people use the phrase "insecure temporary file" when referring to a link following weakness, but other weaknesses can produce insecure temporary files without any symlink involvement at all.
Zip Slip
"Zip slip" is an attack that uses file archives (e.g., ZIP, tar, rar, etc.) that contain filenames with path traversal sequences that cause the files to be written outside of the directory under which the archive is expected to be extracted [REF-1282]. It is most commonly used for relative path traversal (CWE-23) and link following (CWE-59).
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Common Consequences
👁 Section Help
This table specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Impact Details

Read Files or Directories; Modify Files or Directories; Bypass Protection Mechanism

Scope: Confidentiality, Integrity, Access Control
An attacker may be able to traverse the file system to unintended locations and read or overwrite the contents of unexpected files. If the files are used for a security mechanism then an attacker may be able to bypass the mechanism.

Execute Unauthorized Code or Commands

Scope: Other
Windows simple shortcuts, sometimes referred to as soft links, can be exploited remotely since a ".LNK" file can be uploaded like a normal file. This can enable remote execution.
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Potential Mitigations
Phase(s) Mitigation

Architecture and Design

Strategy: Separation of Privilege

Follow the principle of least privilege when assigning access rights to entities in a software system.

Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.
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 Relationships
👁 Section Help
This table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.
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Relevant to the view "Research Concepts" (View-1000)
Nature Type ID Name
ChildOf 👁 Class
Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 		706 Use of Incorrectly-Resolved Name or Reference
ParentOf 👁 Composite
Composite - a Compound Element that consists of two or more distinct weaknesses, in which all weaknesses must be present at the same time in order for a potential vulnerability to arise. Removing any of the weaknesses eliminates or sharply reduces the risk. One weakness, X, can be "broken down" into component weaknesses Y and Z. There can be cases in which one weakness might not be essential to a composite, but changes the nature of the composite when it becomes a vulnerability. 		61 UNIX Symbolic Link (Symlink) Following
ParentOf 👁 Variant
Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. 		62 UNIX Hard Link
ParentOf 👁 Variant
Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. 		64 Windows Shortcut Following (.LNK)
ParentOf 👁 Variant
Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. 		65 Windows Hard Link
ParentOf 👁 Base
Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 		1386 Insecure Operation on Windows Junction / Mount Point
CanFollow 👁 Base
Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 		73 External Control of File Name or Path
CanFollow 👁 Base
Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 		363 Race Condition Enabling Link Following
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Relevant to the view "Software Development" (View-699)
Nature Type ID Name
MemberOf 👁 Category
Category - a CWE entry that contains a set of other entries that share a common characteristic. 		1219 File Handling Issues
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Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (View-1003)
Nature Type ID Name
ChildOf 👁 Class
Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 		706 Use of Incorrectly-Resolved Name or Reference
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Relevant to the view "Architectural Concepts" (View-1008)
Nature Type ID Name
MemberOf 👁 Category
Category - a CWE entry that contains a set of other entries that share a common characteristic. 		1019 Validate Inputs
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Background Details
Soft links are a UNIX term that is synonymous with simple shortcuts on Windows-based platforms.
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Modes Of Introduction
👁 Section Help
The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.
Phase Note
Implementation REALIZATION: This weakness is caused during implementation of an architectural security tactic.
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Applicable Platforms
👁 Section Help
This listing shows possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.
Languages

Class: Not Language-Specific (Undetermined Prevalence)

Operating Systems

Class: Windows (Sometimes Prevalent)

Class: Unix (Often Prevalent)

Technologies

Class: Not Technology-Specific (Undetermined Prevalence)

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Likelihood Of Exploit
Medium
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Selected Observed Examples

Note: this is a curated list of examples for users to understand the variety of ways in which this weakness can be introduced. It is not a complete list of all CVEs that are related to this CWE entry.

Reference Description
Some versions of Perl follow symbolic links when running with the -e option, which allows local users to overwrite arbitrary files via a symlink attack.
Text editor follows symbolic links when creating a rescue copy during an abnormal exit, which allows local users to overwrite the files of other users.
Antivirus update allows local users to create or append to arbitrary files via a symlink attack on a logfile.
Symlink attack allows local users to overwrite files.
Window manager does not properly handle when certain symbolic links point to "stale" locations, which could allow local users to create or truncate arbitrary files.
Second-order symlink vulnerabilities
Second-order symlink vulnerabilities
Symlink in Python program
Setuid product allows file reading by replacing a file being edited with a symlink to the targeted file, leaking the result in error messages when parsing fails.
Signal causes a dump that follows symlinks.
Hard link attack, file overwrite; interesting because program checks against soft links
Hard link and possibly symbolic link following vulnerabilities in embedded operating system allow local users to overwrite arbitrary files.
Server creates hard links and unlinks files as root, which allows local users to gain privileges by deleting and overwriting arbitrary files.
Operating system allows local users to conduct a denial of service by creating a hard link from a device special file to a file on an NFS file system.
Web hosting manager follows hard links, which allows local users to read or modify arbitrary files.
Package listing system allows local users to overwrite arbitrary files via a hard link attack on the lockfiles.
Hard link race condition
Mail client allows remote attackers to bypass the user warning for executable attachments such as .exe, .com, and .bat by using a .lnk file that refers to the attachment, aka "Stealth Attachment."
FTP server allows remote attackers to read arbitrary files and directories by uploading a .lnk (link) file that points to the target file.
FTP server allows remote attackers to read arbitrary files and directories by uploading a .lnk (link) file that points to the target file.
Browser allows remote malicious web sites to overwrite arbitrary files by tricking the user into downloading a .LNK (link) file twice, which overwrites the file that was referenced in the first .LNK file.
".LNK." - .LNK with trailing dot
Rootkits can bypass file access restrictions to Windows kernel directories using NtCreateSymbolicLinkObject function to create symbolic link
File system allows local attackers to hide file usage activities via a hard link to the target file, which causes the link to be recorded in the audit trail instead of the target file.
Web server plugin allows local users to overwrite arbitrary files via a symlink attack on predictable temporary filenames.
A Libcontainer used in Docker Engine allows local users to escape containerization and write to an arbitrary file on the host system via a symlink attack in an image when respawning a container.
"Zip Slip" vulnerability in Go-based Open Container Initiative (OCI) registries product allows writing arbitrary files outside intended directory via symbolic links or hard links in a gzipped tarball.
"Zip Slip" vulnerability in container management product allows writing arbitrary files outside intended directory via a container image (.tar format) with filenames that are symbolic links that point to other files within the same tar file; however, the files being pointed to can also be symbolic links to destinations outside the intended directory, bypassing the initial check.
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Weakness Ordinalities
Ordinality Description
Resultant
(where the weakness is typically related to the presence of some other weaknesses)
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Detection Methods
Method Details

Automated Static Analysis - Binary or Bytecode

According to SOAR [REF-1479], the following detection techniques may be useful:

Cost effective for partial coverage:
  • Bytecode Weakness Analysis - including disassembler + source code weakness analysis

Effectiveness: SOAR Partial

Manual Static Analysis - Binary or Bytecode

According to SOAR [REF-1479], the following detection techniques may be useful:

Cost effective for partial coverage:
  • Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies

Effectiveness: SOAR Partial

Dynamic Analysis with Automated Results Interpretation

According to SOAR [REF-1479], the following detection techniques may be useful:

Cost effective for partial coverage:
  • Web Application Scanner
  • Web Services Scanner
  • Database Scanners

Effectiveness: SOAR Partial

Dynamic Analysis with Manual Results Interpretation

According to SOAR [REF-1479], the following detection techniques may be useful:

Cost effective for partial coverage:
  • Fuzz Tester
  • Framework-based Fuzzer

Effectiveness: SOAR Partial

Manual Static Analysis - Source Code

According to SOAR [REF-1479], the following detection techniques may be useful:

Highly cost effective:
  • Focused Manual Spotcheck - Focused manual analysis of source
  • Manual Source Code Review (not inspections)

Effectiveness: High

Automated Static Analysis - Source Code

According to SOAR [REF-1479], the following detection techniques may be useful:

Cost effective for partial coverage:
  • Source code Weakness Analyzer
  • Context-configured Source Code Weakness Analyzer

Effectiveness: SOAR Partial

Architecture or Design Review

According to SOAR [REF-1479], the following detection techniques may be useful:

Highly cost effective:
  • Formal Methods / Correct-By-Construction
Cost effective for partial coverage:
  • Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

Effectiveness: High
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Functional Areas
  • File Processing
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Affected Resources
  • File or Directory
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Memberships
👁 Section Help
This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
Nature Type ID Name
MemberOf 👁 View
View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).		 635 Weaknesses Originally Used by NVD from 2008 to 2016
MemberOf 👁 Category
Category - a CWE entry that contains a set of other entries that share a common characteristic.		 743 CERT C Secure Coding Standard (2008) Chapter 10 - Input Output (FIO)
MemberOf 👁 Category
Category - a CWE entry that contains a set of other entries that share a common characteristic.		 748 CERT C Secure Coding Standard (2008) Appendix - POSIX (POS)
MemberOf 👁 Category
Category - a CWE entry that contains a set of other entries that share a common characteristic.		 808 2010 Top 25 - Weaknesses On the Cusp
MemberOf 👁 Category
Category - a CWE entry that contains a set of other entries that share a common characteristic.		 877 CERT C++ Secure Coding Section 09 - Input Output (FIO)
MemberOf 👁 View
View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).		 884 CWE Cross-section
MemberOf 👁 Category
Category - a CWE entry that contains a set of other entries that share a common characteristic.		 980 SFP Secondary Cluster: Link in Resource Name Resolution
MemberOf 👁 Category
Category - a CWE entry that contains a set of other entries that share a common characteristic.		 1185 SEI CERT Perl Coding Standard - Guidelines 07. File Input and Output (FIO)
MemberOf 👁 Category
Category - a CWE entry that contains a set of other entries that share a common characteristic.		 1345 OWASP Top Ten 2021 Category A01:2021 - Broken Access Control
MemberOf 👁 Category
Category - a CWE entry that contains a set of other entries that share a common characteristic.		 1404 Comprehensive Categorization: File Handling
MemberOf 👁 Category
Category - a CWE entry that contains a set of other entries that share a common characteristic.		 1436 OWASP Top Ten 2025 Category A01:2025 - Broken Access Control
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Vulnerability Mapping Notes
Usage ALLOWED
(this CWE ID may be used to map to real-world vulnerabilities)
Reason Acceptable-Use

Rationale

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments

Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.
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Notes

Theoretical

Link following vulnerabilities are Multi-factor Vulnerabilities (MFV). They are the combination of multiple elements: file or directory permissions, filename predictability, race conditions, and in some cases, a design limitation in which there is no mechanism for performing atomic file creation operations.

Some potential factors are race conditions, permissions, and predictability.

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Taxonomy Mappings
Mapped Taxonomy Name Node ID Fit Mapped Node Name
PLOVER Link Following
CERT C Secure Coding FIO02-C Canonicalize path names originating from untrusted sources
CERT C Secure Coding POS01-C Check for the existence of links when dealing with files
SEI CERT Perl Coding Standard FIO01-PL CWE More Specific Do not operate on files that can be modified by untrusted users
Software Fault Patterns SFP18 Link in resource name resolution
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References
[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 9, "Symbolic Link Attacks", Page 518. 1st Edition. Addison Wesley. 2006.
[REF-1282] Snyk. "Zip Slip Vulnerability". 2018-06-05.
<https://security.snyk.io/research/zip-slip-vulnerability>.
[REF-1479] Gregory Larsen, E. Kenneth Hong Fong, David A. Wheeler and Rama S. Moorthy. "State-of-the-Art Resources (SOAR) for Software Vulnerability Detection, Test, and Evaluation". 2014-07.
<https://www.ida.org/-/media/feature/publications/s/st/stateoftheart-resources-soar-for-software-vulnerability-detection-test-and-evaluation/p-5061.ashx>. (URL validated: 2025-09-05)
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Content History
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Submissions
Submission Date Submitter Organization
2006-07-19
(CWE Draft 3, 2006-07-19) 		PLOVER
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Modifications
Modification Date Modifier Organization
2025-12-11
(CWE 4.19, 2025-12-11) 		CWE Content Team MITRE
updated Applicable_Platforms, Relationships
2025-09-09
(CWE 4.18, 2025-09-09) 		CWE Content Team MITRE
updated Detection_Factors, References
2023-06-29
(CWE 4.12, 2023-06-29) 		CWE Content Team MITRE
updated Mapping_Notes
2023-04-27
(CWE 4.11, 2023-04-27) 		CWE Content Team MITRE
updated Relationships
2023-01-31
(CWE 4.10, 2023-01-31) 		CWE Content Team MITRE
updated Description
2022-10-13
(CWE 4.9, 2022-10-13) 		CWE Content Team MITRE
updated Alternate_Terms, Background_Details, Observed_Examples, References, Relationship_Notes, Theoretical_Notes
2022-06-28
(CWE 4.8, 2022-06-28) 		CWE Content Team MITRE
updated Relationships
2022-04-28
(CWE 4.7, 2022-04-28) 		CWE Content Team MITRE
updated Research_Gaps
2021-10-28
(CWE 4.6, 2021-10-28) 		CWE Content Team MITRE
updated Relationships
2021-03-15
(CWE 4.4, 2021-03-15) 		CWE Content Team MITRE
updated Relationships
2020-02-24
(CWE 4.0, 2020-02-24) 		CWE Content Team MITRE
updated Relationships
2019-06-20
(CWE 3.3, 2019-06-20) 		CWE Content Team MITRE
updated Relationships
2019-01-03
(CWE 3.2, 2019-01-03) 		CWE Content Team MITRE
updated Taxonomy_Mappings
2017-11-08
(CWE 3.0, 2017-11-08) 		CWE Content Team MITRE
updated Affected_Resources, Applicable_Platforms, Causal_Nature, Common_Consequences, Functional_Areas, Likelihood_of_Exploit, Modes_of_Introduction, Relationships, Taxonomy_Mappings
2015-12-07
(CWE 2.9, 2015-12-07) 		CWE Content Team MITRE
updated Relationships
2014-07-30
(CWE 2.8, 2014-07-31) 		CWE Content Team MITRE
updated Detection_Factors, Relationships, Taxonomy_Mappings
2014-06-23
(CWE 2.7, 2014-06-23) 		CWE Content Team MITRE
updated Common_Consequences, Other_Notes
2012-10-30
(CWE 2.3, 2012-10-30) 		CWE Content Team MITRE
updated Potential_Mitigations
2012-05-11
(CWE 2.2, 2012-05-15) 		CWE Content Team MITRE
updated Common_Consequences, Observed_Examples, References, Relationships
2011-09-13
(CWE 2.1, 2011-09-13) 		CWE Content Team MITRE
updated Relationships, Taxonomy_Mappings
2011-06-01
(CWE 1.13, 2011-06-01) 		CWE Content Team MITRE
updated Common_Consequences
2010-04-05
(CWE 1.8.1, 2010-04-05) 		CWE Content Team MITRE
updated Related_Attack_Patterns
2010-02-16
(CWE 1.8, 2010-02-16) 		CWE Content Team MITRE
updated Potential_Mitigations, Relationships
2009-10-29
(CWE 1.6, 2009-10-29) 		CWE Content Team MITRE
updated Background_Details, Other_Notes
2009-05-27
(CWE 1.4, 2009-05-27) 		CWE Content Team MITRE
updated Description, Name
2009-01-12
(CWE 1.2, 2009-01-12) 		CWE Content Team MITRE
updated Relationships
2008-11-24
(CWE 1.1, 2008-11-25) 		CWE Content Team MITRE
updated Relationships, Taxonomy_Mappings
2008-09-08
(CWE 1.0, 2008-09-09) 		CWE Content Team MITRE
updated Alternate_Terms, Applicable_Platforms, Relationships, Other_Notes, Relationship_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2008-07-01
(CWE 1.0, 2008-09-09) 		Eric Dalci Cigital
updated Time_of_Introduction
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Previous Entry Names
Change Date Previous Entry Name
2009-05-27 Failure to Resolve Links Before File Access (aka 'Link Following')
2008-04-11 Link Following
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Page Last Updated: April 30, 2026

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