CVE-2026-40686

Name	CVE-2026-40686
Description	In Exim before 4.99.2, when utf8 operators are enabled, there is an out-of-bounds read if large UTF-8 trailing characters are present (malformed UTF-8 header data). Information might be divulged within an error message produced during handling of an unrelated e-mail message.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
exim4 (PTS)	bullseye	4.94.2-7+deb11u3	vulnerable
	bullseye (security)	4.94.2-7+deb11u4	vulnerable
	bookworm, bookworm (security)	4.96-15+deb12u7	vulnerable
	trixie	4.98.2-1	vulnerable
	forky, sid	4.99.2-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
exim4	source	(unstable)	4.99.2-1

Notes

[trixie] - exim4 <no-dsa> (Minor issue)
[bookworm] - exim4 <no-dsa> (Minor issue)
Fixed by: https://code.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eecf6372efc