CVE-2026-6691 Details
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.
A heap buffer overflow vulnerability has been identified in the MongoDB C Driver's integration with Cyrus SASL. This issue arises from unsafe string copying during the canonicalization of usernames. The vulnerability can be exploited by providing untrusted input in the username field of a MongoDB URI that includes the GSSAPI authentication mechanism. The buffer overflow occurs before any authentication is performed or network traffic is transmitted.
Users can upgrade to MongoDB C Driver versions 2.2.0 or 2.1.3, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed May 6, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://jira.mongodb.org/browse/CDRIVER-6134 | [email protected] | PatchVendor AdvisoryIssue Tracking |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-787 | Out-of-bounds Write | [email protected] |
| CWE-120 | Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| mongodb c driver | >= 2.1.0, < 2.1.2 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 18, 2026 | Initial Analysis | [email protected] |
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 6, 2026 | New CVE Received | [email protected] |