{"id":"CVE-2026-84971","aliases":["DEBIAN-CVE-2026-84971","EUVD-2026-70507","GHSA-pxxc-vwf4-r3mr","UBUNTU-CVE-2026-84971"],"status":"published","title":"Persistent client crash loop via undersized FLE2 insert-update ciphertext in decryption path","description":"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.","severity":{"version":"4.0","score":7.1,"vector":"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","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00259,"percentile":0.1772,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-617"],"published":"2026-09-03T14:57:35Z","modified":"2026-10-28T02:30:25Z","fixes":[{"ecosystem":"Debian:14","package":"libmongocrypt","fixed_in":["1.20.4-1"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Debian:12","package":"libmongocrypt","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.10.0-1","1.10.1-1","1.11.0-1","1.12.0-1","1.13.0-1","1.13.1-1","1.13.2-1","1.16.0-1","1.17.0-1","1.17.3-1","1.18.1-1","1.18.2-1","1.19.0-1","1.19.1-1","1.20.0-1","1.20.1-1","1.20.2-1","1.20.3-1","1.20.4-1","1.7.2-1","1.8.2-1","1.8.4-1","1.9.1-1"]},{"source":"osv","ecosystem":"Debian:13","package":"libmongocrypt","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.13.2-1","1.13.2-1+deb13u1","1.16.0-1","1.17.0-1","1.17.3-1","1.18.1-1","1.18.2-1","1.19.0-1","1.19.1-1","1.20.0-1","1.20.1-1","1.20.2-1","1.20.3-1","1.20.4-1"]},{"source":"osv","ecosystem":"Debian:14","package":"libmongocrypt","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.20.4-1"}]}],"versions":["1.13.2-1","1.16.0-1","1.17.0-1","1.17.3-1","1.18.1-1","1.18.2-1","1.19.0-1","1.19.1-1","1.20.0-1","1.20.1-1","1.20.2-1","1.20.3-1"]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"libmongocrypt","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.2.1-1","1.2.2-1","1.3.0-1","1.3.0-1ubuntu1"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"libmongocrypt","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.7.2-1","1.8.2-1","1.8.4-1","1.8.4-1build2","1.8.4-1build3"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"libmongocrypt","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.17.0-1","1.19.0-1","1.19.1-1","1.20.0-1","1.20.1-1build1","1.20.2-1"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"libmongocrypt","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.13.2-1","1.17.0-1"]}],"products":[{"vendor":"mongodb","product":"libmongocrypt"}],"references":[{"url":"https://jira.mongodb.org/browse/MONGOCRYPT-971","tags":["Vendor Advisory","Issue Tracking","Patch","web","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-84971","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-pxxc-vwf4-r3mr"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/84xxx/CVE-2026-84971.json","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-84971","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-84971","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-84971","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-84971","title":"Persistent client crash loop via undersized FLE2 insert-update ciphertext in decryption path","description":"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.","status":"published","published":"2026-09-03T14:57:35.521Z","modified":"2026-09-03T15:10:21.808Z","cvss":[{"version":"4.0","score":7.1,"vector":"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","level":"high","assessor":"cna"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"cna"}],"cwes":["CWE-617"],"updated_at":"2026-11-02T14:20:08.734143Z"}],"euvd":[{"id":"EUVD-2026-70507","description":"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.","status":"published","published":"2026-09-03T14:57:35Z","modified":"2026-09-03T15:10:21Z","cvss":[{"version":"4.0","score":7.1,"vector":"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","level":"high"}],"updated_at":"2026-11-02T18:01:13.671159Z"}],"ghsa":[{"id":"GHSA-pxxc-vwf4-r3mr","title":"Improper handling of an unexpected value size in the decryption path of a client-side encryption...","description":"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.","status":"published","published":"2026-09-03T15:32:24Z","modified":"2026-09-03T15:32:28Z","cvss":[{"version":"4.0","score":7.1,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium"}],"cwes":["CWE-617"],"updated_at":"2026-11-02T15:11:19.170234Z"}],"nvd":[{"id":"CVE-2026-84971","description":"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.","status":"published","published":"2026-09-03T15:17:36.547Z","modified":"2026-09-17T13:59:13.18Z","cvss":[{"version":"4.0","score":7.1,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high","assessor":"secondary"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"secondary"}],"cwes":["CWE-617"],"updated_at":"2026-11-02T14:12:43.399612Z"}],"osv":[{"id":"CVE-2026-84971","title":"Persistent client crash loop via undersized FLE2 insert-update ciphertext in decryption path","description":"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.","status":"published","published":"2026-09-03T14:57:35.521Z","modified":"2026-10-28T02:30:25.383354615Z","cvss":[{"version":"4.0","score":7.1,"vector":"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","level":"high"}],"cwes":["CWE-617"],"updated_at":"2026-11-02T15:45:18.482949Z"},{"id":"DEBIAN-CVE-2026-84971","description":"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.","status":"published","published":"2026-09-03T15:17:36.547Z","modified":"2026-10-01T03:03:43.619454158Z","cvss":[{"version":"4.0","score":7.1,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high"}],"updated_at":"2026-11-02T15:46:05.022702Z"},{"id":"UBUNTU-CVE-2026-84971","description":"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.","status":"published","published":"2026-09-03T15:17:00Z","modified":"2026-10-17T13:01:13.022223517Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium"},{"version":"4.0","score":7.1,"vector":"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","level":"high"}],"updated_at":"2026-11-02T16:57:24.828975Z"}]}}