{"id":"UBUNTU-CVE-2025-49600","details":"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.","modified":"2026-05-20T16:23:32.792976463Z","published":"2025-07-04T15:15:00Z","upstream":["CVE-2025-49600"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2025-49600"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2025-49600"},{"type":"REPORT","url":"https://github.com/Mbed-TLS/mbedtls-docs/blob/main/security-advisories/mbedtls-security-advisory-2025-06-3.md"}],"affected":[{"package":{"name":"mbedtls","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/mbedtls?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.6.2-3ubuntu1"],"ecosystem_specific":{"binaries":[{"binary_version":"3.6.2-3ubuntu1","binary_name":"libmbedcrypto16"},{"binary_version":"3.6.2-3ubuntu1","binary_name":"libmbedtls21"},{"binary_version":"3.6.2-3ubuntu1","binary_name":"libmbedx509-7"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-49600.json"}},{"package":{"name":"mbedtls","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/mbedtls?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.6.2-3ubuntu1","3.6.5-0.1ubuntu1","3.6.5-0.1ubuntu2"],"ecosystem_specific":{"binaries":[{"binary_version":"3.6.5-0.1ubuntu2","binary_name":"libmbedcrypto16"},{"binary_version":"3.6.5-0.1ubuntu2","binary_name":"libmbedtls21"},{"binary_version":"3.6.5-0.1ubuntu2","binary_name":"libmbedx509-7"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-49600.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N"},{"type":"Ubuntu","score":"medium"}]}