CVE-2026-40685

EUVD-2026-26443
In Exim before 4.99.2, when JSON lookup is enabled, an out-of-bounds heap write can occur when a JSON operator encounters malformed JSON in an untrusted header, because of an incorrect implementation of \ skipping.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTPrimary
6.5 MEDIUM
NETWORK
HIGH
NONE
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
Base Score
CVSS 3.x
EPSS Score
Percentile: 23%
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
ignored
focal
Fixed 4.93-13ubuntu1.12+esm1
released
jammy
Fixed 4.95-4ubuntu2.7
released
noble
Fixed 4.97-4ubuntu4.4
released
questing
Fixed 4.98.2-1ubuntu2.1
released
resolute
Fixed 4.99.1-1ubuntu1.1
released
trusty
ignored
xenial
ignored
Common Weakness Enumeration
References
https://code.exim.org/exim/exim/commit/9fdc057e71b87c87a0d3d2288b2810a0efaaba57
https://exim.org/static/doc/security/CVE-2026-40685.txt
https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40685.assessment
https://www.openwall.com/lists/oss-security/2026/04/30/21