{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "cpe": "cpe:2.3:a:mongodb:libmongocrypt:*:*:*:*:*:*:*:*",
            "extracted_events": [
              {
                "introduced": "1.7.0"
              },
              {
                "fixed": "1.20.4"
              }
            ],
            "source": "CPE_RANGE"
          },
          "events": [
            {
              "introduced": "76a17191ae96c24c1b984a763f4a2b8fe5935ce8"
            },
            {
              "fixed": "ab45a792fd995db28b6fde3e730edf6a7a90fbf4"
            }
          ],
          "repo": "https://github.com/mongodb/libmongocrypt",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "mongodb",
    "cwe_ids": [
      "CWE-617"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/84xxx/CVE-2026-84971.json",
    "unresolved_ranges": [
      {
        "extracted_events": [
          {
            "introduced": "1.7.0"
          },
          {
            "fixed": "1.20.4"
          }
        ],
        "source": "AFFECTED_FIELD"
      }
    ]
  },
  "details": "Improper handling of an unexpected value size in the decryption path of a client-side encryption library can cause a failed internal check that terminates the process using the library. A party able to place a suitably formed encrypted value where an application will decrypt it, or able to control the responses the application receives, may cause that application to stop running.",
  "id": "CVE-2026-84971",
  "modified": "2026-09-19T03:30:45.884285433Z",
  "published": "2026-09-03T14:57:35.521Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://jira.mongodb.org/browse/MONGOCRYPT-971"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/84xxx/CVE-2026-84971.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-84971"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Persistent client crash loop via undersized FLE2 insert-update ciphertext in decryption path"
}