CVE-2026-74942

Name	CVE-2026-74942
Description	Privilege escalation in the Remote Settings Client component. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.
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)
References	DLA-4750-1, DSA-6451-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
firefox (PTS)	sid	154.0-1	fixed
firefox-esr (PTS)	bullseye	115.14.0esr-1~deb11u1	vulnerable
	bullseye (security)	140.14.0esr-1~deb11u1	fixed
	bookworm	140.12.0esr-1~deb12u1	vulnerable
	bookworm (security)	140.14.0esr-1~deb12u1	fixed
	trixie	140.12.0esr-1~deb13u1	vulnerable
	trixie (security)	140.14.0esr-1~deb13u1	fixed
	forky	140.13.0esr-2	vulnerable
	sid	140.14.0esr-2	fixed
thunderbird (PTS)	bullseye	1:115.12.0-1~deb11u1	vulnerable
	bullseye (security)	1:140.13.0esr-2~deb11u1	vulnerable
	bookworm	1:140.12.0esr-1~deb12u1	vulnerable
	bookworm (security)	1:140.13.0esr-2~deb12u1	vulnerable
	trixie	1:140.12.0esr-1~deb13u1	vulnerable
	trixie (security)	1:140.13.0esr-2~deb13u1	vulnerable
	forky	1:140.13.0esr-2	vulnerable
	sid	1:140.14.0esr-1	fixed

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

Package	Type	Release	Fixed Version	Origin
firefox	source	(unstable)	154.0-1
firefox-esr	source	bullseye	140.14.0esr-1~deb11u1	DLA-4750-1
firefox-esr	source	bookworm	140.14.0esr-1~deb12u1	DLA-4750-1
firefox-esr	source	trixie	140.14.0esr-1~deb13u1	DSA-6451-1
firefox-esr	source	(unstable)	140.14.0esr-2
thunderbird	source	(unstable)	1:140.14.0esr-1

Notes

https://www.mozilla.org/en-US/security/advisories/mfsa2026-74/#CVE-2026-74942
https://www.mozilla.org/en-US/security/advisories/mfsa2026-76/#CVE-2026-74942
https://www.mozilla.org/en-US/security/advisories/mfsa2026-79/#CVE-2026-74942