5.9

CVE-2026-84966: mongodb c_driver

CVSS: 5.9v4.0MediumAnalyzed
AliasesDEBIAN-CVE-2026-84966UBUNTU-CVE-2026-84966
Published 03-09-2026Last modified 03-09-2026
Open JSON

Vulnerability summary

CVE-2026-84966 is a medium (CVSS 5.9) vulnerability in mongodb c_driver. EPSS estimates a 0.14% chance of exploitation in the next 30 days, higher than 3.1% of scored vulnerabilities.

Overall risk
24/100
0100
Low · default modelHow is this calculated?
CVSS score
5.9/10
010
Medium · v4.0 (CVE.org)
EPSS score
0.14%
0%100%
Low · +0.03 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

An incorrect numeric type conversion in the BSON document building component of the MongoDB C++ Driver may cause a length value to be interpreted incorrectly. When an application supplies an extremely large, non-terminated field name to the builder, the library may read memory outside the intended buffer and terminate the calling process. No authentication is required, but the calling application must pass the oversized name in a specific form.

CVSS metrics

7 scores · 4 sources · 2 versions

EPSS trend

Probability

0.14%

Chance of exploitation in the next 30 days

Percentile

3%

Versus all other CVEs

30-day change

+0.03 pp

From 0.11% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.14%

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
  • mongo-cxx-driver< 4.5.2-1
Mongodb1 product
  • c_driver≥ 3.2.0, < 4.5.2 | ≥ 3.0.0, < 4.5.2
Ubuntu1 product
  • mongo-cxx-driverAll versions (No fix recorded)

3 vendors · 3 products

References

4 links