CVE-2026-40684

HIGH 7.5CVE-2026-40684 · Published 30/04/2026 · updated 17/06/2026

In short

CVE-2026-40684 is a HIGH (CVSS 7.5) vulnerability affecting exim (exim).
Chance of exploitation in the next 30 days (EPSS): 0.36%, higher than 30.0% of all vulnerabilities.
Fix: update to 4.99.2 or later.

Package	Affected versions	Patched versions
exim exim	`< 4.99.2`	`4.99.2`

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.

References

code.exim.org/exim/exim/commit/628bbaca7672748d941a12e7cd5f0122a4e18c81 · Patch
exim.org/static/doc/security/CVE-2026-40684.txt · Broken Link
exim.org/static/doc/security/cve-2026-04.1/CVE2026-40684.assessment · Vendor Advisory
openwall.com/lists/oss-security/2026/04/30/21 · Mailing List
openwall.com/lists/oss-security/2026/05/01/11

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Package

Affected versions

Patched versions

exim

< 4.99.2

4.99.2

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