VulnerabilityUndergoing Analysis

CVE-2026-84966

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.

MEDIUM 5.9EPSS 0.11%

Does this matter?

Lower severity and a low EPSS score (0.11%). Track it; it rarely justifies an emergency change on its own.

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 4.0: 5.9 MEDIUMCVSS:4.0/AV:L/AC:L/AT:P/PR:N/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/M
EPSS: 0.11% probability · 1th percentile
CISA KEV: Not listed
Weakness: CWE-681
Source: cna@mongodb.com

References

https://jira.mongodb.org/browse/CXX-3548

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.