CVE-2026-126136

Name	CVE-2026-126136
Description	For Exchange accounts using EWS or Microsoft Graph with OAuth2 authentication, Thunderbird sent the OAuth2 access token to the server even when the configured server URL used unencrypted HTTP. An attacker able to observe network traffic could obtain the token and use it to access the user's mailbox until the token expired. An attacker positioned on the network during account setup could cause such a URL to be configured. This vulnerability was fixed in Thunderbird 160 and Thunderbird 153.7.
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)	1:153.6.0esr-1~deb12u2	vulnerable
	trixie	1:140.12.0esr-1~deb13u1	vulnerable
	trixie (security)	1:153.6.0esr-1~deb13u1	vulnerable
	forky	1:153.5.0esr-1	vulnerable
	sid	1:153.7.0esr-1	fixed

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

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
thunderbird	source	(unstable)	1:153.7.0esr-1

https://www.mozilla.org/en-US/security/advisories/mfsa2026-129/#CVE-2026-126136