CVE-2026-84971
6.5 · MEDIUMImproper 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.
Overview
CVE-2026-84971 is a medium-severity vulnerability affecting mongodb libmongocrypt. It was published on September 3, 2026 and has a CVSS 3.1 base score of 6.5 (MEDIUM).
This vulnerability has a CVSS 3.1 base score of 6.5, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.
Technical 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
Check the references section for vendor advisories and patches from mongodb. Update libmongocrypt to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| mongodb | libmongocrypt | >= 1.7.0, < 1.20.4 | Affected |
References
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Frequently asked questions
What is CVE-2026-84971?
CVE-2026-84971 is a medium-severity vulnerability affecting mongodb libmongocrypt. It was published on September 3, 2026 and has a CVSS 3.1 base score of 6.5 (MEDIUM).
How severe is CVE-2026-84971?
This vulnerability has a CVSS 3.1 base score of 6.5, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.
How do I fix or remediate CVE-2026-84971?
Check the references section for vendor advisories and patches from mongodb. Update libmongocrypt to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-84971?
CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-84971 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.
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