CVE-2026-84971
MEDIUMDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Exploit Intelligence
Low risk: more likely to be exploited than 6% of all known CVEs.
References
Related Vulnerabilities
Other CWE-617 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2020-8617 | High | 7.5 | 93% | - | Fix |
| CVE-2020-36222 | High | 7.5 | 78% | - | Fix |
| CVE-2006-5779 | High | 7.5 | 76% | - | Fix |
| CVE-2021-27212 | High | 7.5 | 64% | - | Fix |
| CVE-2018-5740 | High | 7.5 | 60% | - | Fix |
| CVE-2023-28425 | Medium | 5.5 | 55% | - | Fix |
Common questions
How do I fix CVE-2026-84971?
Upgrade libmongocrypt on debian unstable to 1.20.4-1 or later.
Is CVE-2026-84971 being actively exploited?
Not that we know of. CVE-2026-84971 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.16% is the estimated probability that it will be exploited in the next 30 days. That is higher than 6% of all scored CVEs.
How severe is CVE-2026-84971?
CVE-2026-84971 has a CVSS v3 base score of 6.5, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-84971 affect?
Published advisories record a fix for libmongocrypt (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-09-17.