CVE-2026-110247

Name	CVE-2026-110247
Description	Several buffer-growth sites in libmime performed size arithmetic in 32-bit types without overflow checks. On a sufficiently large message the growth guard could fail open, or the buffer could be reallocated smaller than required, and a subsequent memcpy would then write attacker-controlled data across adjacent heap allocations. This vulnerability was fixed in Thunderbird 158.
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
thunderbird (PTS)	bookworm	1:140.12.0esr-1~deb12u1	vulnerable
	bookworm (security)	1:140.17.0esr-1~deb12u1	vulnerable
	trixie	1:140.12.0esr-1~deb13u1	vulnerable
	trixie (security)	1:140.17.0esr-1~deb13u1	vulnerable
	forky, sid	1:153.4.0esr-1	vulnerable

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

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
thunderbird	source	(unstable)	(unfixed)

https://www.mozilla.org/en-US/security/advisories/mfsa2026-109/#CVE-2026-110247