CVE-2026-34876

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.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact NONE

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-ccm-finish-boundary-check/	Vendor Advisory
https://mbed-tls.readthedocs.io/en/latest/tech-updates/security-advisories/	Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:trustedfirmware:mbed_tls:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-04-02 16:16

Updated : 2026-07-24 21:10

NVD link : CVE-2026-34876

Mitre link : CVE-2026-34876

CVE.ORG link : CVE-2026-34876

JSON object : View

Products Affected

trustedfirmware

mbed_tls

CWE

CWE-125

Out-of-bounds Read

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