CVE-2026-40686 - 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)

Back Back to CVE browser

MEDIUM

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)

Published Apr 30, 2026

5.3

MEDIUM

CVSS 3.1

EPSS 0.40%

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.

Affected products

Vendor Exim Product Exim Default
unaffected
- Version
  0
  Status
  affected
  Constraints
  <4.99.2

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor

Product

Default status

Versions

Exim

unaffected

Version	Status	Constraints
0	affected	<4.99.2

Remediation

No remediation recorded yet.

Weaknesses (1)

CWE-125

Out-of-bounds Read

References (5)

https://code.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eecf6372efc
Patch
https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-26444
Advisory
https://exim.org/static/doc/security/CVE-2026-40686.txt
Broken Link
https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40686.assessment
Vendor Advisory
https://www.openwall.com/lists/oss-security/2026/04/30/21
Mailing ListThird Party Advisory

Link	Providers	Tags
https://code.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eecf6372efc		Patch
https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-26444		Advisory
https://exim.org/static/doc/security/CVE-2026-40686.txt		Broken Link
https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40686.assessment		Vendor Advisory
https://www.openwall.com/lists/oss-security/2026/04/30/21		Mailing ListThird Party Advisory