CVE-2026-34873

EUVD-2026-18064
An issue was discovered in Mbed TLS 3.5.0 through 4.0.0. Client impersonation can occur while resuming a TLS 1.3 session.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTPrimary
9.1 CRITICAL
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Base Score
CVSS 3.x
EPSS Score
Percentile: 11%
Affected Products (NVD)
VendorProductVersion
armmbed_tls
3.5.0 ≤
𝑥
< 3.6.6
armmbed_tls
4.0.0 ≤
𝑥
< 4.1.0
𝑥
= Vulnerable software versions
Debian logo
Debian Releases
Debian Product
Codename
mbedtls
bookworm
vulnerable
bullseye
vulnerable
bullseye (security)
vulnerable
forky
vulnerable
sid
3.6.6-0.1
fixed
trixie
vulnerable
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-client-impersonation-while-resuming-tls13-session/