CVE-2026-84971Persistent 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.

Data: CVE.org, NVD, CISA KEV, FIRST EPSS, Ubuntu. Published as the sources state it, in English.

Affected products and versions

References and patches

• https://jira.mongodb.org/browse/MONGOCRYPT-971 Vendor AdvisoryIssue TrackingPatch