CVE-2026-6986

Name	CVE-2026-6986
Description	A security vulnerability has been detected in Cesanta Mongoose up to 7.20. This issue affects the function mg_aes_gcm_decrypt of the file /src/tls_aes128.c of the component GCM Authentication Tag Handler. Such manipulation leads to improper verification of cryptographic signature. The attack may be performed from remote. A high complexity level is associated with this attack. The exploitability is assessed as difficult. The exploit has been disclosed publicly and may be used. Upgrading to version 7.21 is capable of addressing this issue. It is advisable to upgrade the affected component. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.
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
mongoose (PTS)	forky, sid	7.21+ds-2	fixed
swupdate (PTS)	bullseye	2020.11-2+deb11u1	vulnerable
	bookworm	2022.12+dfsg-4+deb12u2	vulnerable
	trixie	2024.12.1+dfsg-3+deb13u2	vulnerable
	forky, sid	2025.12+dfsg-10	fixed

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

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
mongoose	source	(unstable)	(not affected)
swupdate	source	(unstable)	2025.12+dfsg-10

Notes

- mongoose <not-affected> (Fixed before or with initial upload)
[trixie] - swupdate <no-dsa> (Minor issue)
[bookworm] - swupdate <no-dsa> (Minor issue)
[bullseye] - swupdate <postponed> (Minor issue)