{"id":"DEBIAN-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":"2026-09-12T10:00:16.297300357Z","published":"2026-04-02T16:16:26.180Z","upstream":["CVE-2026-34876"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-34876"}],"affected":[{"package":{"name":"mbedtls","ecosystem":"Debian:12","purl":"pkg:deb/debian/mbedtls?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.28.3-1","2.28.4-1","2.28.5-1","2.28.6-1","2.28.7-1","2.28.7-1.1","2.28.7-1.1~exp1","2.28.8-1","3.6.0-1","3.6.0-2","3.6.0-3","3.6.2-1","3.6.2-2","3.6.2-3","3.6.3-1","3.6.4-1","3.6.4-2","3.6.5-0.1","3.6.5-0.1~deb13u1","3.6.6-0.1","3.6.6-0.1~deb13u1","3.6.7-2","3.6.7-3"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-34876.json"}},{"package":{"name":"mbedtls","ecosystem":"Debian:13","purl":"pkg:deb/debian/mbedtls?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.6.6-0.1~deb13u1"}]}],"versions":["3.6.4-2","3.6.5-0.1","3.6.5-0.1~deb13u1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-34876.json"}},{"package":{"name":"mbedtls","ecosystem":"Debian:14","purl":"pkg:deb/debian/mbedtls?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.6.6-0.1"}]}],"versions":["3.6.4-2","3.6.5-0.1","3.6.5-0.1~deb13u1","3.6.6-0.1~deb13u1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-34876.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"}]}