# CVE-2026-34877: mbedtls: An issue was discovered in Mbed TLS versions from 2.19.0 up to 3.6.5, Mbed TLS 4.0.0

CVE-2026-34877 is fixed in mbedtls on 1 platform by DEBIAN-CVE-2026-34877 (version 3.6.6-0.1), released April 2, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2026-34877
- Priority: Urgent
- CVSS: 9.8 (critical)
- EPSS: 0.0044
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 2, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | mbedtls Debian 14 | 3.6.6-0.1 | [DEBIAN-CVE-2026-34877](https://patchblox.com/security/data/fix/linux/debian-cve-2026-34877.md) | Apr 2, 2026 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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