Mongodb Libmongocrypt
CVE-2026-84971
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.
What this means for your business
- It affects Mongodb Libmongocrypt. It matters if your company, or a supplier that handles your data, runs it.
- An attacker can use it remotely, over a network, with an ordinary user login, and without anyone at your company clicking anything.
- FIRST's prediction model gives it a 0.2% chance of attack attempts being seen in the next 30 days, ranking above 5% of all known flaws.
What to do
- 1Check whether your company or your suppliers run Mongodb Libmongocrypt, and which version. The affected versions are listed further down this page.
- 2If you do, apply the vendor's fix. A patch or vendor advisory has been published.
Fastnexa security experts
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Scoring
- CVSS
- 6.5 (v3.1)
- Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H- CVSS v4
- 7.1
- Weakness
- CWE-617
- Assigned by
- cna@mongodb.com
Dates
- Published
- 2026-09-03
- Last modified
- 2026-09-17
- Sources
- NVD
Affected products
- Mongodb Libmongocrypt1.7.0 - 1.20.4
As listed in the NVD configuration data. Not a statement about your estate.