UnratedFix available

DEBIAN-CVE-2026-34876

Type: advisorySource: OSV1 source record

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.

Announced 2 Apr 2026Group revision 1

Original source ↗

DEBIAN-CVE-2026-34876

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: osv:DEBIAN-CVE-2026-34876

mbedtls

Source reference: /affected/0/package/name

Affected versions: 2.28.3-1
Source reference: /affected/0/versions
2.28.4-1
Source reference: /affected/0/versions
2.28.5-1
Source reference: /affected/0/versions
2.28.6-1
Source reference: /affected/0/versions
2.28.7-1
Source reference: /affected/0/versions
2.28.7-1.1
Source reference: /affected/0/versions
2.28.7-1.1~exp1
Source reference: /affected/0/versions
2.28.8-1
Source reference: /affected/0/versions
3.6.0-1
Source reference: /affected/0/versions
3.6.0-2
Source reference: /affected/0/versions
3.6.0-3
Source reference: /affected/0/versions
3.6.2-1
Source reference: /affected/0/versions
3.6.2-2
Source reference: /affected/0/versions
3.6.2-3
Source reference: /affected/0/versions
3.6.3-1
Source reference: /affected/0/versions
3.6.4-1
Source reference: /affected/0/versions
3.6.4-2
Source reference: /affected/0/versions
3.6.5-0.1
Source reference: /affected/0/versions
3.6.5-0.1~deb13u1
Source reference: /affected/0/versions
3.6.6-0.1
Source reference: /affected/0/versions
3.6.6-0.1~deb13u1
Source reference: /affected/0/versions
3.6.7-2
Source reference: /affected/0/versions
3.6.7-3
Source reference: /affected/0/versions
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

mbedtls

Source reference: /affected/1/package/name

Affected versions: 3.6.4-2
Source reference: /affected/1/versions
3.6.5-0.1
Source reference: /affected/1/versions
3.6.5-0.1~deb13u1
Source reference: /affected/1/versions
Fixed versions: 3.6.6-0.1~deb13u1
Source reference: /affected/1/ranges
Prerequisites: Not stated in this record

mbedtls

Source reference: /affected/2/package/name

Affected versions: 3.6.4-2
Source reference: /affected/2/versions
3.6.5-0.1
Source reference: /affected/2/versions
3.6.5-0.1~deb13u1
Source reference: /affected/2/versions
3.6.6-0.1~deb13u1
Source reference: /affected/2/versions
Fixed versions: 3.6.6-0.1
Source reference: /affected/2/ranges
Prerequisites: Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          }
        ]
      }
    ],
    "package": {
      "name": "mbedtls",
      "purl": "pkg:deb/debian/mbedtls?arch=source&distro=bookworm",
      "ecosystem": "Debian:12"
    },
    "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"
    ],
    "database_specific": {
      "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-34876.json"
    },
    "ecosystem_specific": {
      "urgency": "not yet assigned"
    }
  },
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          },
          {
            "fixed": "3.6.6-0.1~deb13u1"
          }
        ]
      }
    ],
    "package": {
      "name": "mbedtls",
      "purl": "pkg:deb/debian/mbedtls?arch=source&distro=trixie",
      "ecosystem": "Debian:13"
    },
    "versions": [
      "3.6.4-2",
      "3.6.5-0.1",
      "3.6.5-0.1~deb13u1"
    ],
    "database_specific": {
      "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-34876.json"
    },
    "ecosystem_specific": {
      "urgency": "not yet assigned"
    }
  },
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          },
          {
            "fixed": "3.6.6-0.1"
          }
        ]
      }
    ],
    "package": {
      "name": "mbedtls",
      "purl": "pkg:deb/debian/mbedtls?arch=source&distro=forky",
      "ecosystem": "Debian:14"
    },
    "versions": [
      "3.6.4-2",
      "3.6.5-0.1",
      "3.6.5-0.1~deb13u1",
      "3.6.6-0.1~deb13u1"
    ],
    "database_specific": {
      "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-34876.json"
    },
    "ecosystem_specific": {
      "urgency": "not yet assigned"
    }
  }
]

Publisher severity

No explicit severity was provided.

Event: #56398 · Revision 1
Added to Heist Feed: Sun, 25 Oct 2026 16:35:57 GMT
Publisher date: Thu, 02 Apr 2026 16:16:26 GMT

Read the original announcement

Revision history

25 Oct 2026DEBIAN-CVE-2026-34876 · Revision 1Source updated