Quick answers
- Is CVE-2026-84971 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-84971 being exploited in the wild.
- How severe is CVE-2026-84971?
- Medium severity, with a CVSS score of 6.5, published 3 September 2026.
- Which products and versions are affected?
- MongoDB Libmongocrypt before 1.20.4.
- Is there a fix for CVE-2026-84971?
- A patch was published on 2026-09-03: Fixed in version 1.20.4 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-84971 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-84971?
- Check whether you run MongoDB Libmongocrypt at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is a client-side denial of service flaw in the decryption path of libmongocrypt caused by improper handling of unexpectedly small (undersized) encrypted payload values. When the library attempts to decrypt a malformed payload with insufficient data, it fails an internal validation check and aborts the process. An attacker with the ability to place a crafted encrypted value where an application will decrypt it, or control network responses, can trigger this abort condition. The issue was fixed in version 1.20.4 of libmongocrypt.
Affected products
- MongoDB libmongocrypt before 1.20.4
Timeline
- 2026-09-03: disclosed
- 2026-09-03: patched: Fixed in version 1.20.4