CVE-2026-84971

Persistent client crash loop via undersized FLE2 insert-update ciphertext in decryption path

Published Sep 3, 2026 CVSS 4.0 · 7.1 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

Sign in to view the affected projects.

Advisories

No advisories available
History
Type Values Removed Values Added
CPEs cpe:2.3:a:mongodb:libmongocrypt:*:*:*:*:*:*:*:*
Type Values Removed Values Added
First Time appeared Mongodb
Mongodb libmongocrypt
Vendors & Products Mongodb
Mongodb libmongocrypt
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title Persistent client crash loop via undersized FLE2 insert-update ciphertext in decryption path
Weaknesses CWE-617
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
mongodb
Published
Updated
Sep 3, 2026, 3:10 PM
Reserved
Sep 2, 2026, 5:58 PM
Status
Analyzed
Published
Sep 3, 2026, 3:17 PM
Modified
Sep 17, 2026, 1:59 PM