CVE-2026-40684

EUVD-2026-26442
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.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTPrimary
5.9 MEDIUM
NETWORK
HIGH
NONE
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Base Score
CVSS 3.x
EPSS Score
Percentile: 27%
Affected Products (NVD)
VendorProductVersion
eximexim
𝑥
< 4.99.2
𝑥
= Vulnerable software versions
Debian logo
Debian Releases
Debian Product
Codename
exim4
bookworm
4.96-15+deb12u9
fixed
bookworm (security)
4.96-15+deb12u10
fixed
bullseye
unimportant
bullseye (security)
unimportant
forky
4.99.4-1
fixed
sid
4.99.4-1
fixed
trixie
4.98.2-1+deb13u2
fixed
trixie (security)
4.98.2-1+deb13u3
fixed
Ubuntu logo
Ubuntu Releases
Ubuntu Product
Codename
exim4
bionic
not-affected
focal
not-affected
jammy
not-affected
noble
not-affected
questing
not-affected
resolute
not-affected
trusty
not-affected
xenial
not-affected
Common Weakness Enumeration
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