Executive brief
Mbed TLS is a widely used encryption library that helps secure data transmission for embedded devices and applications. A flaw in its CCM encryption component could allow an attacker to read sensitive information from the system's memory. This could lead to the exposure of internal security keys or other private data, potentially compromising the confidentiality of encrypted communications.
Technical details
An out-of-bounds read vulnerability exists in the mbedtls_ccm_finish() function within library/ccm.c. The root cause is a failure to validate the 'tag_len' parameter against the internal 16-byte authentication buffer (ctx->y) before performing a memcpy operation. In Mbed TLS 3.x, this function is part of the public multipart CCM API, allowing an attacker who can control API parameters to read adjacent memory in the mbedtls_ccm_context structure. This leaked data may include nonce/counter data, mode parameters, and block cipher context state. The issue is resolved in Mbed TLS 3.6.6 and 4.0.0.
Affected products
- TrustedFirmware Mbed TLS 3.1.0 to 3.6.5
Timeline
- 2026-03-31: advisory: Vendor security advisory released
- 2026-04-02: disclosed: CVE published to NVD