CVE-2026-40686
Detail
Description
In Exim before 4.99.2, when utf8 operators are enabled, there is an out-of-bounds read if large UTF-8 trailing characters are present (malformed UTF-8 header data). Information might be divulged within an error message produced during handling of an unrelated e-mail message.
Metrics
NVD enrichment efforts reference publicly available information to associate
vector strings. CVSS information contributed by other sources is also
displayed.
CVSS 4.0 Severity and Vector Strings:
NVD assessment
not yet provided.
CVSS 3.x Severity and Vector Strings:
Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
CVSS 2.0 Severity and Vector Strings:
Base
Score:
NVD assessment
not yet provided.
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Weakness Enumeration
| CWE-ID |
CWE Name |
Source |
|
CWE-125
|
Out-of-bounds Read |
MITRE
|
Change History
5 change records found show changes
CVE Modified by CISA-ADP
6/17/2026 6:45:34 AM
| Action |
Type |
Old Value |
New Value |
| Added |
SSVC |
{"timestamp":"2026-05-01T14:27:01.351716Z","id":"CVE-2026-40686","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}
|
CVE Modified by MITRE
6/17/2026 6:45:34 AM
| Action |
Type |
Old Value |
New Value |
| Added |
Affected |
[{"vendor":"Exim","product":"Exim","defaultStatus":"unaffected","versions":[{"version":"0","lessThan":"4.99.2","versionType":"semver","status":"affected"}]}]
|
Initial Analysis by NIST
5/01/2026 1:44:15 PM
| Action |
Type |
Old Value |
New Value |
| Added |
CVSS V3.1 |
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
|
| Added |
CPE Configuration |
OR
*cpe:2.3:a:exim:exim:*:*:*:*:*:*:*:* versions up to (excluding) 4.99.2
|
| Added |
Reference Type |
MITRE: https://code.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eecf6372efc Types: Patch
|
| Added |
Reference Type |
MITRE: https://exim.org/static/doc/security/CVE-2026-40686.txt Types: Broken Link
|
| Added |
Reference Type |
MITRE: https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40686.assessment Types: Vendor Advisory
|
| Added |
Reference Type |
MITRE: https://www.openwall.com/lists/oss-security/2026/04/30/21 Types: Mailing List, Third Party Advisory
|
CVE Modified by MITRE
4/30/2026 10:16:04 PM
| Action |
Type |
Old Value |
New Value |
| Added |
Reference |
https://exim.org/static/doc/security/CVE-2026-40686.txt
|
| Removed |
Reference |
https://exim.org/static/doc/security/CVE-2025-40686.txt
|
New CVE Received from MITRE
4/30/2026 6:16:25 PM
| Action |
Type |
Old Value |
New Value |
| Added |
Description |
In Exim before 4.99.2, when utf8 operators are enabled, there is an out-of-bounds read if large UTF-8 trailing characters are present (malformed UTF-8 header data). Information might be divulged within an error message produced during handling of an unrelated e-mail message.
|
| Added |
CVSS V3.1 |
AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
|
| Added |
CWE |
CWE-125
|
| Added |
Reference |
https://code.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eecf6372efc
|
| Added |
Reference |
https://exim.org/static/doc/security/CVE-2025-40686.txt
|
| Added |
Reference |
https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40686.assessment
|
| Added |
Reference |
https://www.openwall.com/lists/oss-security/2026/04/30/21
|
Quick Info
CVE Dictionary Entry: CVE-2026-40686 NVD
Published Date: 04/30/2026 NVD
Last Modified: 06/17/2026
Source: MITRE
|
