CVE-2026-40684

HighCVSS 7.5/10Last modified Nov 11, 2026

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.

Metrics

CVSS 3.1 7.5/10CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Weakness enumeration

CWE-684

Affected software

Vendor	Product	Versions
Exim	Exim	< 4.99.2

References

https://code.exim.org/exim/exim/commit/628bbaca7672748d941a12e7cd5f0122a4e18c81Patch
https://exim.org/static/doc/security/CVE-2026-40684.txtBroken Link
https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40684.assessmentVendor Advisory
https://www.openwall.com/lists/oss-security/2026/04/30/21Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2026/05/01/11

Timeline

Published: Apr 30, 2026
Last modified: Nov 11, 2026
NVD status: Modified

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