{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "cpe": "cpe:2.3:a:trustedfirmware:mbed_tls:*:*:*:*:*:*:*:*",
            "extracted_events": [
              {
                "introduced": "3.1.0"
              },
              {
                "fixed": "3.6.6"
              }
            ],
            "source": "CPE_RANGE"
          },
          "events": [
            {
              "introduced": "d65aeb37349ad1a50e0f6c9b694d4b5290d60e49"
            },
            {
              "fixed": "0bebf8b8c7f07abe3571ded48a11aa907a1ffb20"
            }
          ],
          "repo": "https://github.com/mbed-tls/mbedtls",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "mitre",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34876.json",
    "unresolved_ranges": [
      {
        "extracted_events": [
          {
            "introduced": "3.x"
          },
          {
            "fixed": "3.6.6"
          }
        ],
        "source": "DESCRIPTION"
      }
    ]
  },
  "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.",
  "id": "CVE-2026-34876",
  "modified": "2026-07-15T01:48:51.063969949Z",
  "published": "2026-04-02T00:00:00Z",
  "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"
    }
  ],
  "schema_version": "1.8.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ]
}