CVSS 5.9 · MEDIUM
CVE-2026-40684
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.
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Score: 5.9(MEDIUM)
Vector:
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HAV: NETWORK
AC: HIGH
PR: NONE
UI: NONE
S: UNCHANGED
C: NONE
I: NONE
A: HIGH
Weakness (CWE):
CWE-684EPSS
Probability of exploitation (next 30 days): 0.0007 (0.1%)
Percentile: 21.6%
EPSS: 2026-05-06
Affects
exim:eximTechnical 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.
Published: 4/30/2026, 10:16:25 PM
Last modified: 5/1/2026, 6:16:15 PM
References
- https://code.exim.org/exim/exim/commit/628bbaca7672748d941a12e7cd5f0122a4e18c81
- https://exim.org/static/doc/security/CVE-2026-40684.txt
- https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40684.assessment
- https://www.openwall.com/lists/oss-security/2026/04/30/21
- http://www.openwall.com/lists/oss-security/2026/05/01/11