7.1

CVE-2026-84971: mongodb libmongocrypt Reachable Assertion

CVSS: 7.1v4.0HighAnalyzed
AliasesUBUNTU-CVE-2026-84971DEBIAN-CVE-2026-84971
Published 03-09-2026Last modified 03-09-2026
Open JSON

Vulnerability summary

CVE-2026-84971 is a high (CVSS 7.1) Reachable Assertion vulnerability in mongodb libmongocrypt. EPSS estimates a 0.26% chance of exploitation in the next 30 days, higher than 16.5% of scored vulnerabilities.

Overall risk
28/100
0100
Medium · default modelHow is this calculated?
CVSS score
7.1/10
010
High · v4.0 (CVE.org)
EPSS score
0.26%
0%100%
Low · +0.10 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 03-09-2026
    PublishedVulnerability first disclosed.
  2. 03-09-2026
    Last modifiedVulnerability information updated.

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 metrics

7 scores · 4 sources · 2 versions

EPSS trend

Probability

0.26%

Chance of exploitation in the next 30 days

Percentile

17%

Versus all other CVEs

30-day change

+0.10 pp

From 0.16% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.26%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Debian1 product
  • libmongocryptAll versions (No fix recorded) | < 1.20.4-1
Mongodb1 product
Ubuntu1 product
  • libmongocryptAll versions (No fix recorded)

3 vendors · 3 products

References

4 links