{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "cpe": "cpe:2.3:a:mongodb:c_driver:*:*:*:*:*:mongodb:*:*",
            "extracted_events": [
              {
                "introduced": "2.1.0"
              },
              {
                "fixed": "2.1.2"
              }
            ],
            "source": "CPE_RANGE"
          },
          "events": [
            {
              "introduced": "163250d2cc81c532a6315f6ad7e01bf35da9401d"
            },
            {
              "fixed": "81c27ddadd54e80d9743dee0e8b7a0a862aa6ab5"
            }
          ],
          "repo": "https://github.com/mongodb/mongo-c-driver",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "mongodb",
    "cwe_ids": [
      "CWE-120"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/6xxx/CVE-2026-6691.json",
    "unresolved_ranges": [
      {
        "extracted_events": [
          {
            "introduced": "2.1.0"
          },
          {
            "last_affected": "2.1.2"
          }
        ],
        "source": "AFFECTED_FIELD"
      }
    ]
  },
  "details": "The MongoDB C Driver's Cyrus SASL integration performs unsafe string copying during username canonicalization, enabling a heap buffer overflow before any authentication or network traffic. This may be triggered by passing untrusted input in the username of a MongoDB URI with authMechanism=GSSAPI.",
  "id": "CVE-2026-6691",
  "modified": "2026-07-08T05:37:02.650596002Z",
  "published": "2026-05-06T15:08:23.671Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://jira.mongodb.org/browse/CDRIVER-6134"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/6xxx/CVE-2026-6691.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-6691"
    }
  ],
  "schema_version": "1.7.5",
  "severity": [
    {
      "score": "CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "MongoDB C Driver Cyrus SASL Canonicalization Buffer Overflow"
}