Deserialization in Arm Mbed TLS
CVE-2026-34877
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.007 (53.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 53rd percentile — 53.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.007 · change: +0.003
Affected products
- Arm Mbed TLS
- Trustedfirmware Mbed TLS — versions 4.0.0
Weakness classification (CWE)
References
- mbed-tls.readthedocs.io/en/latest/security-advisories/ (Vendor Advisory)
- mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory… (Vendor Advisory)
Frequently asked questions
- What is CVE-2026-34877?
- CVE-2026-34877 is a critical-severity vulnerability in Arm Mbed TLS, classified under CWE-250. CVSS score: 9.8/10. Published 2026-04-02.
- How severe is CVE-2026-34877?
- Critical severity. CVSS v3 base score is 9.8 out of 10.