Heap-based buffer overflow in MongoDB driver for C - CVE-2026-6691
Published: August 18, 2026
Vulnerability identifier: #VU144151
CSH Severity: High
CVSS v4: 8.4 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-6691
CWE-ID: CWE-122
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to a heap-based buffer overflow in the MongoDB C Driver Cyrus SASL integration when canonicalizing the username from a MongoDB URI with authMechanism=GSSAPI. A remote attacker can supply a specially crafted username value to execute arbitrary code.
User interaction is required to pass untrusted input in the username of a MongoDB URI.
Affected software
MongoDB driver for C
How to mitigate CVE-2026-6691
Install security update from vendor's website.
MongoDB driver for C - update to 2.2.0