Bug 2376428 (CVE-2025-49600)

Summary: CVE-2025-49600 mbedtls: MbedTLS LMS Signature Forgery via Fault Injection
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in mbedtls. The `mbedtls_lms_verify` function may accept forged Leighton-Micali signatures when hash computation fails and internal error conditions are not properly checked. This flaw allows an attacker with physical access to create invalid signatures. This issue occurs because return values from hash computations are not validated, potentially bypassing signature verification. Consequently, an attacker can forge signatures without authentication or authorization.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2376715, 2376711, 2376712, 2376713, 2376714, 2382562    
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Description OSIDB Bzimport 2025-07-04 15:01:36 UTC 
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.