CVE-2026-2303: mongo-go-driver Buffer Overflow Flaw

CVE-2026-2303 Overview

CVE-2026-2303 is an Out-of-Bounds Read vulnerability affecting the mongo-go-driver repository. The C wrapper implementation for CGo bindings used in GSSAPI (Kerberos) authentication on Linux and macOS contains a heap out-of-bounds read vulnerability due to incorrect assumptions about string termination in the GSSAPI standard. Since GSSAPI buffers are not guaranteed to be null-terminated or have extra padding, this results in reading one byte past the allocated heap buffer.

Critical Impact

Attackers with network access and limited privileges could potentially exploit this memory safety issue to read sensitive data from adjacent heap memory, potentially leading to information disclosure or integrity compromise of authentication-related data.

Affected Products

• mongo-go-driver with GSSAPI (Kerberos) authentication enabled
• Linux systems using mongo-go-driver CGo bindings for Kerberos
• macOS systems using mongo-go-driver CGo bindings for Kerberos

Discovery Timeline

• 2026-02-10 - CVE-2026-2303 published to NVD
• 2026-02-10 - Last updated in NVD database

Technical Details for CVE-2026-2303

Vulnerability Analysis

This vulnerability exists in the CGo bindings implementation that wraps GSSAPI (Kerberos) authentication functionality for the MongoDB Go driver. The root issue stems from incorrect assumptions about how string data is handled within GSSAPI buffers.

The GSSAPI standard does not guarantee that buffers will be null-terminated or contain extra padding bytes. However, the C wrapper code appears to assume null-termination when processing these buffers, resulting in a heap out-of-bounds read of one byte beyond the allocated memory region. While the out-of-bounds read is limited to a single byte, this type of memory safety issue can have unpredictable consequences depending on heap layout and the nature of adjacent memory allocations.

The vulnerability requires network access and some level of authentication (low privileges) to exploit, with user interaction also required. The primary security impact is to integrity, as the vulnerability could allow manipulation of authentication-related processes.

Root Cause

The root cause is a CWE-183 (Permissive List of Allowed Inputs) issue combined with improper memory boundary handling. The C wrapper implementation makes incorrect assumptions about the termination of GSSAPI buffers. The GSSAPI specification does not mandate null-termination for buffer contents, but the code incorrectly assumes this guarantee exists, leading to reading one byte beyond the allocated heap buffer when processing authentication data.

Attack Vector

The attack vector is network-based, requiring an attacker to have low-level privileges and some user interaction. An attacker could potentially craft malicious GSSAPI authentication responses that trigger the out-of-bounds read condition. The exploitation scenario involves:

1. An attacker with network access targeting a system using mongo-go-driver with Kerberos authentication
2. Manipulation of GSSAPI authentication exchanges to trigger the vulnerable code path
3. The C wrapper code reads one byte past the allocated buffer boundary
4. Depending on heap layout, this could lead to information disclosure or authentication integrity issues

The vulnerability mechanism involves improper handling of GSSAPI buffer boundaries in the CGo wrapper code. When processing Kerberos authentication data, the code assumes string termination that the GSSAPI standard does not guarantee, leading to the out-of-bounds memory access. For technical implementation details, refer to the MongoDB Driver Issue Tracker.

Detection Methods for CVE-2026-2303

Indicators of Compromise

• Unexpected crashes or memory corruption errors in applications using mongo-go-driver with Kerberos authentication
• Abnormal authentication failures or behavior during GSSAPI/Kerberos exchanges with MongoDB
• Memory access violations reported by address sanitizer tools in applications using the vulnerable driver

Detection Strategies

• Deploy application-level monitoring to detect unusual patterns in Kerberos authentication flows
• Enable memory safety tools (AddressSanitizer, Valgrind) during development and testing to catch out-of-bounds reads
• Monitor for unexpected behavior in applications using mongo-go-driver GSSAPI authentication

Monitoring Recommendations

• Implement logging for all GSSAPI authentication events in MongoDB driver usage
• Monitor system logs for memory-related errors from applications using Kerberos authentication with MongoDB
• Track driver version deployments across your infrastructure to identify vulnerable installations

How to Mitigate CVE-2026-2303

Immediate Actions Required

• Review all applications using mongo-go-driver with GSSAPI (Kerberos) authentication enabled
• Monitor the MongoDB Driver Issue Tracker for patch availability
• Consider temporarily switching to alternative authentication methods if GSSAPI/Kerberos is not strictly required

Patch Information

Patch information should be monitored through the official MongoDB JIRA issue tracker at the MongoDB Driver Issue Tracker. Users should upgrade to the patched version of mongo-go-driver once it becomes available from MongoDB.

Workarounds

• If GSSAPI/Kerberos authentication is not required, disable it and use alternative MongoDB authentication mechanisms such as SCRAM-SHA-256
• Implement network segmentation to limit exposure of systems using vulnerable authentication configurations
• Deploy additional monitoring and intrusion detection for systems that must continue using GSSAPI authentication

# Configuration example
# Verify current mongo-go-driver version
go list -m go.mongodb.org/mongo-driver

# Consider switching to non-GSSAPI authentication in connection string
# Replace Kerberos auth with SCRAM-SHA-256 where possible
# mongodb://user:password@host:27017/?authMechanism=SCRAM-SHA-256