Out-of-bounds read in mbedtls_lms_import_public_key()

Title	Out-of-bounds read in mbedtls_lms_import_public_key()
CVE	CVE-2025-49601
Date	2025-06-30
Affects	Mbed TLS 3.3.0 through 3.6.3
Not affected	Mbed TLS 3.6.4 and later 3.6 versions and upcoming TF-PSA-Crypto 1.0 and later versions
Impact	Denial of service and possible information disclosure
Severity	MEDIUM
Credits	Found and reported by Linh Le and Ngan Nguyen from Calif.

Vulnerability

An LMS public key starts with a 4-byte type indicator. The function mbedtls_lms_import_public_key() reads this type indicator before validating the size of its input.

If a public key is shorted than 4 bytes, the function performs a buffer overread of up to 4 bytes, resulting in undefined behavior. In practice this can only cause a crash and, at most, leak whether those four bytes match a fixed value. No arbitrary code execution is possible.

Impact

Denial of service and possible information disclosure of a few bytes of adjacent memory. No arbitrary code execution or large‐scale memory disclosure is possible.

Affected versions

Mbed TLS 3.3.0 through 3.6.3

Resolution

Affected users should upgrade to Mbed TLS 3.6.4 or upcoming TF-PSA-Crypto 1.0 or later.

Work-around

Validate that the key provided to mbedtls_lms_import_public_key() is at least 4 bytes long.