CVE-2026-34877

Name	CVE-2026-34877
Description	An issue was discovered in Mbed TLS versions from 2.19.0 up to 3.6.5, Mbed TLS 4.0.0. Insufficient protection of serialized SSL context or session structures allows an attacker who can modify the serialized structures to induce memory corruption, leading to arbitrary code execution. This is caused by Incorrect Use of Privileged APIs.
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
mbedtls (PTS)	bullseye	2.16.9-0.1	vulnerable
	bullseye (security)	2.16.9-0.1+deb11u3	vulnerable
	bookworm	2.28.3-1	vulnerable
	trixie	3.6.5-0.1~deb13u1	vulnerable
	forky, sid	3.6.5-0.1	vulnerable

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

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

https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-serialized-data/