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HIGH · 7.8

CVE-2026-6691

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...

Vulnerability Description

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.

CVSS Score

7.8

HIGH

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH

Affected Products

VendorProductVersions
MongodbC Driver>= 2.1.0, < 2.1.2

Related Weaknesses (CWE)

CWE-120CWE-787

References

FAQ

What is CVE-2026-6691?

CVE-2026-6691 is a vulnerability with a CVSS score of 7.8 (HIGH). 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...

How severe is CVE-2026-6691?

CVE-2026-6691 has been rated HIGH with a CVSS base score of 7.8/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-6691?

Check the references section above for vendor advisories and patch information. Affected products include: Mongodb C Driver.