CVE-2026-6691 HIGH

CVE-2026-6691: MongoDB C Driver Cyrus SASL Canonicalization Buffer Overflow

Vendor Mongodb Inc.
Product MongoDB C Driver
Weakness CWE-120
Published May 6, 2026
Last update May 7, 2026

CVSS base score

8.6/10
Attack vector Local
Attack complexity Low
Privileges required None
User interaction None
Confidentiality
Integrity

CVSS vector

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

May 6, 2026 CVE published
May 7, 2026 Record updated