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CVE-2026-34876 Detail

Description

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.


Metrics

NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.
CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
N/A
NVD assessment not yet provided.

References to Advisories, Solutions, and Tools

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URL Source(s) Tag(s)
https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-ccm-finish-boundary-check/ MITRE
https://mbed-tls.readthedocs.io/en/latest/tech-updates/security-advisories/ MITRE

Weakness Enumeration

CWE-ID CWE Name Source
CWE-125 Out-of-bounds Read CISA-ADP  

Change History

2 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2026-34876
NVD Published Date:
04/02/2026
NVD Last Modified:
04/02/2026
Source:
MITRE