CVE-2026-6691

EUVD-2026-27838
The MongoDB C Driver's Cyrus SASL integration performs unsafe string copying during username canonicalization, enabling a heap buffer overflow before any authentication or network traffic. This may be triggered by passing untrusted input in the username of a MongoDB URI with authMechanism=GSSAPI.
Classic Buffer Overflow
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
mongodbCNA
7.8 HIGH
LOCAL
LOW
NONE
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Base Score
CVSS 3.x
EPSS Score
Percentile: 3%
Early Detection
Affected products identified ahead of NVD analysis through intelligence sources.
VendorProductVersionSource
mongodbc_driver
2.1.0 ≤
𝑥
≤ 2.1.2
CNA
Debian logo
Debian Releases
Debian Product
Codename
mongo-c-driver
bookworm
no-dsa
bullseye
postponed
bullseye (security)
vulnerable
forky
2.3.0-1
fixed
sid
2.3.0-1
fixed
trixie
no-dsa
Common Weakness Enumeration
Vulnerability Media Exposure
References
https://jira.mongodb.org/browse/CDRIVER-6134