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Vulnerability record · CVE-2026-84971 · published 3 September 2026

CVE-2026-84971: Mongodb libmongocrypt vulnerability

Mongodb · Libmongocrypt

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.

7.1 CVSS 4.0 High EPSS 0.26% · top 84.2% CWE-617 · CWE-617
7.1CVSS 4.0 base score
0.26%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
1References
17 Sep 2026Last modified by NVD

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://jira.mongodb.org/browse/MONGOCRYPT-971 Vendor AdvisoryIssue TrackingPatch

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

5.7CVE-2026-84962Mongodb libmongocrypt vulnerabilityAn unauthorized user with key vault write access may cause an authorized client to issue arbitrary authenticated Google Cloud KMS API calls under the…EPSS 0.19%2.0CVE-2026-81523Mongodb libmongocrypt injection vulnerabilityA missing input-validation issue in MongoDB libmongocrypt's automatic-encryption context setup allows a caller-supplied database identifier to be acc…EPSS 0.10%

Source: NIST National Vulnerability Database (record CVE-2026-84971), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.