CVE-2026-40684

MEDIUM

5.9

Description

In Exim before 4.99.2, on systems using musl libc (not glibc), an attacker can crash the connection instance when malformed DNS data is present in PTR records. This is caused by a dn_expand oddity in octal printing.

CVE Details

CVSS v3.1 Score5.9

SeverityMEDIUM

CVSS VectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack VectorNETWORK

ComplexityHIGH

Privileges RequiredNONE

User InteractionNONE

Published4/30/2026

Last Modified5/1/2026

Sourcenvd

Honeypot Sightings0

Affected Products

exim:exim

Weaknesses (CWE)

CWE-684

References

https://code.exim.org/exim/exim/commit/628bbaca7672748d941a12e7cd5f0122a4e18c81(cve@mitre.org)

https://exim.org/static/doc/security/CVE-2026-40684.txt(cve@mitre.org)

https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40684.assessment(cve@mitre.org)

https://www.openwall.com/lists/oss-security/2026/04/30/21(cve@mitre.org)

http://www.openwall.com/lists/oss-security/2026/05/01/11(af854a3a-2127-422b-91ae-364da2661108)

IOC Correlations

No correlations recorded

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