What’s Vulnerable › Vulnerabilities
CVE-2026-84971: Persistent client crash loop via undersized FLE2 insert-update ciphertext in decryption path
- Severity: medium (CVSS 6.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.3% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-09-03 · updated 2026-09-17
- Weakness: CWE-617
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.
Affected products
- MongoDB libmongocrypt: from 1.7.0 before 1.20.4 — fixed in 1.20.4
How to fix
Upgrade to a fixed version: MongoDB libmongocrypt 1.20.4. Check the vendor advisory for mitigations.
References
Get alerted when CVE-2026-84971 or the next vulnerability affects your stack