CVE-2025-49600
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.
Scoring
- Severity
- MEDIUM
- CVSS base score
- 4.9
- CVSS vector
- CVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N
- EPSS probability
- 0.13%
- CWE
- CWE-325
- Published
- 2025-07-04
- Last modified
- 2026-03-13
Affected products
- Mbed mbedtls
Weakness type
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