What is CVE-2026-34873?

CVE-2026-34873 is a critical-severity vulnerability in Trustedfirmware Mbed_tls, classified under Improper Authentication. CVSS score: 9.1/10. Published 2026-04-01.

How severe is CVE-2026-34873?

Critical severity. CVSS v3 base score is 9.1 out of 10.

Auth bypass in Trustedfirmware Mbed_tls

CVE-2026-34873

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.

Vulnerability class: Broken Authentication

EPSS: 0.000 (12.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

Affected products

Trustedfirmware Mbed_tls
N/a — versions n/a

Weakness classification (CWE)

CWE-287 — Improper Authentication

References

cve@mitre.org (Vendor Advisory)
cve@mitre.org (Vendor Advisory)

Frequently asked questions

What is CVE-2026-34873?: CVE-2026-34873 is a critical-severity vulnerability in Trustedfirmware Mbed_tls, classified under Improper Authentication. CVSS score: 9.1/10. Published 2026-04-01.
How severe is CVE-2026-34873?: Critical severity. CVSS v3 base score is 9.1 out of 10.