# CVE-2025-49600: mbedtls: In MbedTLS 3.3.0 before 3.6.4, mbedtls_lms_verify may accept invalid signatures if hash computation fails and interna...

CVE-2025-49600 is fixed in mbedtls on 1 platform, first by DEBIAN-CVE-2025-49600, released July 4, 2025. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2025-49600
- Priority: Routine
- CVSS: 4.9 (medium)
- EPSS: 0.0016
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 4, 2025

## Description

In MbedTLS 3.3.0 before 3.6.4, mbedtls_lms_verify may accept invalid signatures if hash computation fails and internal errors go unchecked, enabling LMS (Leighton-Micali Signature) forgery in a fault scenario. Specifically, unchecked return values in mbedtls_lms_verify allow an attacker (who can induce a hardware hash accelerator fault) to bypass LMS signature verification by reusing stale stack data, resulting in acceptance of an invalid signature. In mbedtls_lms_verify, the return values of the internal Merkle tree functions create_merkle_leaf_value and create_merkle_internal_value are not checked. These functions return an integer that indicates whether the call succeeded or not. If a failure occurs, the output buffer (Tc_candidate_root_node) may remain uninitialized, and the result of the signature verification is unpredictable. When the software implementation of SHA-256 is used, these functions will not fail. However, with hardware-accelerated hashing, an attacker could use fault injection against the accelerator to bypass verification.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | mbedtls Debian 13.5 (trixie) | 3.6.4-1 | [DEBIAN-CVE-2025-49600](https://patchblox.com/security/data/fix/linux/debian-cve-2025-49600.md) | Jul 4, 2025 |
| Linux | mbedtls Debian 14 | 3.6.4-1 | [DEBIAN-CVE-2025-49600](https://patchblox.com/security/data/fix/linux/debian-cve-2025-49600.md) | Jul 4, 2025 |
| Linux | mbedtls opensuse-leap 16.0 | 3.6.6-bp160.1.1 | [OPENSUSE-SU-2026:21144-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21144-1.md) | Jun 22, 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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