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.
Advisories
Source ID Title
EUVD EUVD EUVD-2025-20080 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.
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Thu, 17 Jul 2025 16:00:00 +0000

Type Values Removed Values Added
First Time appeared Arm
Arm mbed Tls
CPEs cpe:2.3:a:arm:mbed_tls:*:*:*:*:*:*:*:*
Vendors & Products Arm
Arm mbed Tls

Tue, 08 Jul 2025 15:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 04 Jul 2025 15:00:00 +0000

Type Values Removed Values Added
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.
Weaknesses CWE-325
References
Metrics cvssV3_1

{'score': 4.9, 'vector': 'CVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: mitre

Published:

Updated: 2025-07-08T14:36:23.748Z

Reserved: 2025-06-06T00:00:00.000Z

Link: CVE-2025-49600

cve-icon Vulnrichment

Updated: 2025-07-08T14:35:09.273Z

cve-icon NVD

Status : Analyzed

Published: 2025-07-04T15:15:22.277

Modified: 2025-07-17T15:59:03.633

Link: CVE-2025-49600

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2025-07-13T21:47:58Z