CVE-2026-34876
HighCVSS 7.5Exploitation Probability (EPSS)
Low risk32th percentile - higher than 32% of all known CVEs
Summary
Mbed TLS 3.x before 3.6.6 has an out-of-bounds read vulnerability in mbedtls_ccm_finish() due to missing validation of the tag_len parameter. An attacker can obtain adjacent CCM context data.
Risk Assessment
An attacker can read sensitive data from memory, potentially leading to disclosure of keys or other secrets.
Recommendation
Upgrade Mbed TLS to version 3.6.6 or later.
Other vulnerabilities in Mbed TLS
Original NVD description (English source)
An issue was discovered in Mbed TLS 3.x before 3.6.6. An out-of-bounds read vulnerability in mbedtls_ccm_finish() in library/ccm.c allows attackers to obtain adjacent CCM context data via invocation of the multipart CCM API with an oversized tag_len parameter. This is caused by missing validation of the tag_len parameter against the size of the internal 16-byte authentication buffer. The issue affects the public multipart CCM API in Mbed TLS 3.x, where mbedtls_ccm_finish() can be invoked directly by applications. In Mbed TLS 4.x versions prior to the fix, the same missing validation exists in the internal implementation; however, the function is not exposed as part of the public API. Exploitation requires application-level invocation of the multipart CCM API.