CVE-2026-34877

EUVD-2026-18394
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.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTPrimary
9.8 CRITICAL
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Base Score
CVSS 3.x
EPSS Score
Percentile: 35.55%
Affected Products (NVD)
VendorProductVersion
armmbed_tls
2.19.0 ≤
𝑥
< 3.6.6
trustedfirmwarembed_tls
4.0.0
𝑥
= Vulnerable software versions
Debian logo
Debian Releases
Debian Product
Codename
mbedtls
bookworm
unimportant
bullseye
2.16.9-0.1
fixed
bullseye (security)
2.16.9-0.1+deb11u4
fixed
forky
3.6.7-3
fixed
sid
3.6.7-3
fixed
trixie
unimportant
Ubuntu logo
Ubuntu Releases
Ubuntu Product
Codename
mbedtls
bionic
needs-triage
focal
needs-triage
jammy
needs-triage
noble
needs-triage
questing
ignored
resolute
needs-triage
xenial
ignored
Common Weakness Enumeration
References
https://mbed-tls.readthedocs.io/en/latest/security-advisories/
https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-serialized-data/