Executive brief
Mbed TLS is a widely used security library that provides encryption and secure communication for embedded devices. A flaw in how it handles certain digital signature keys could allow an attacker to cause a system crash or potentially view a very small amount of internal memory. This could lead to a temporary service outage for the affected device, though it does not allow for full system takeover.
Technical details
An out-of-bounds read (CWE-125) exists in the mbedtls_lms_import_public_key() function. The root cause is a failure to validate that the input buffer is at least 4 bytes long before attempting to read a 32-bit type indicator field. An attacker can exploit this by providing a truncated LMS public key buffer (fewer than 4 bytes). This results in a buffer overread of up to 4 bytes, which can lead to undefined behavior, typically manifesting as a crash (DoS) or the leakage of whether adjacent memory matches specific fixed values. The vulnerability is present in Mbed TLS versions 3.3.0 through 3.6.3 and is fixed in version 3.6.4.
Affected products
- Arm Mbed TLS 3.3.0 to 3.6.3
- TrustedFirmware Mbed TLS 3.3.0 to 3.6.3
Timeline
- 2025-06-30: advisory: Vendor security advisory released
- 2025-07-04: disclosed: CVE published