{"id":"CVE-2026-84971","summary":"Persistent client crash loop via undersized FLE2 insert-update ciphertext in decryption path","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.","modified":"2026-09-19T03:47:24.037152519Z","published":"2026-09-03T14:57:35.521Z","database_specific":{"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"}],"cna_assigner":"mongodb","cwe_ids":["CWE-617"]},"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"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/mongodb/libmongocrypt","events":[{"introduced":"76a17191ae96c24c1b984a763f4a2b8fe5935ce8"},{"fixed":"ab45a792fd995db28b6fde3e730edf6a7a90fbf4"}],"database_specific":{"extracted_events":[{"introduced":"1.7.0"},{"fixed":"1.20.4"}],"source":"CPE_RANGE","cpe":"cpe:2.3:a:mongodb:libmongocrypt:*:*:*:*:*:*:*:*"}}],"versions":["1.20.3","1.20.2","1.20.1","1.20.0","pymongocrypt-1.18.1","pymongocrypt-1.18.0","pymongocrypt-1.18.0.dev0","pymongocrypt-1.17.0","pymongocrypt-1.16.0","pymongocrypt-1.15.1","pymongocrypt-1.15.0","pymongocrypt-1.14.1","pymongocrypt-1.14.0","pymongocrypt-1.13.0","pymongocrypt-1.12.2","pymongocrypt-1.12.2rc4","pymongocrypt-1.12.2rc2","pymongocrypt-1.12.2rc1","pymongocrypt-1.2.2rc0","pymongocrypt-1.12.1","pymongocrypt-1.12.0","pymongocrypt-1.11.0","java-1.11.0","csharp-v1.11.0","pymongocrypt-1.10.1","csharp-v1.10.0","pymongocrypt-1.10.0","1.10.0b1","1.10.0b0","pymongocrypt-1.9.1","node-v6.0.1","csharp-v1.9.0","pymongocrypt-1.9.0","csharp-v1.8.2","csharp-v1.8.1","pymongocrypt-1.8.0","node-v6.0.0","node-v6.0.0-alpha.3","node-v6.0.0-alpha.2","pymongocrypt-1.7.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-84971.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","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"}]}