{"id":"CVE-2026-34876","details":"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.","modified":"2026-07-15T01:48:51.063969949Z","published":"2026-04-02T00:00:00Z","related":["openSUSE-SU-2026:10498-1"],"database_specific":{"unresolved_ranges":[{"extracted_events":[{"introduced":"3.x"},{"fixed":"3.6.6"}],"source":"DESCRIPTION"}],"cna_assigner":"mitre","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34876.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34876.json"},{"type":"ADVISORY","url":"https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-ccm-finish-boundary-check/"},{"type":"ADVISORY","url":"https://mbed-tls.readthedocs.io/en/latest/tech-updates/security-advisories/"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-34876"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/mbed-tls/mbedtls","events":[{"introduced":"d65aeb37349ad1a50e0f6c9b694d4b5290d60e49"},{"fixed":"0bebf8b8c7f07abe3571ded48a11aa907a1ffb20"}],"database_specific":{"cpe":"cpe:2.3:a:trustedfirmware:mbed_tls:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"3.1.0"},{"fixed":"3.6.6"}],"source":"CPE_RANGE"}}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-34876.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"}]}