CVE-2025-6709: MongoDB Server DoS Vulnerability

CVE-2025-6709 Overview

The MongoDB Server is susceptible to a denial of service vulnerability due to improper handling of specific date values in JSON input when using OIDC authentication. This vulnerability allows attackers to send malicious JSON payloads through the mongo shell, triggering an invariant failure that causes a complete server crash.

Critical Impact

Unauthenticated attackers can remotely crash MongoDB Server instances configured with OIDC authentication by sending specially crafted JSON payloads containing malformed date values, leading to service unavailability and potential data access disruption.

Affected Products

• MongoDB Server v7.0 versions prior to 7.0.17
• MongoDB Server v8.0 versions prior to 8.0.5
• MongoDB Server v6.0 versions prior to 6.0.21 (requires authentication to exploit)

Discovery Timeline

• 2025-06-26 - CVE-2025-6709 published to NVD
• 2025-09-15 - Last updated in NVD database

Technical Details for CVE-2025-6709

Vulnerability Analysis

This vulnerability stems from improper input validation (CWE-20) in MongoDB Server's JSON parsing logic when processing date values during OIDC (OpenID Connect) authentication flows. The server fails to properly sanitize and validate specific date value formats within JSON payloads, leading to an invariant assertion failure when encountering unexpected date representations.

When a malicious payload is processed, the server's internal validation logic encounters a condition it was not designed to handle, triggering an invariant check failure. This defensive programming mechanism, intended to catch programming errors during development, causes an immediate server crash in production environments rather than gracefully handling the malformed input.

The vulnerability is particularly concerning for MongoDB Server versions 7.0 and 8.0, where exploitation can occur without prior authentication when OIDC authentication is enabled. In version 6.0, the same underlying parsing flaw exists, but the authentication requirement provides an additional layer of protection, limiting exploitation to authenticated users.

Root Cause

The root cause lies in improper input validation within MongoDB's JSON date parsing routines used during OIDC authentication processing. The server expects date values to conform to specific formats, but lacks comprehensive boundary checking and error handling for edge cases. When specific date values are encountered that fall outside expected parameters, the invariant assertion fails rather than returning an error response, resulting in process termination.

Attack Vector

The attack can be executed remotely over the network without requiring any user interaction. An attacker can connect to an exposed MongoDB instance and use the mongo shell or equivalent client to send crafted JSON payloads containing malicious date values. The attack targets the OIDC authentication pathway, meaning systems configured for OpenID Connect authentication are at risk.

The exploitation process involves:

1. Identifying MongoDB instances with OIDC authentication enabled
2. Crafting a JSON payload with specific malformed date values that trigger the parsing error
3. Sending the payload to the target server through the mongo shell or a compatible client
4. The server processes the payload, encounters the invalid date value, and triggers an invariant failure
5. The MongoDB server process crashes, causing denial of service

For MongoDB versions 7.0 and 8.0, this attack can be performed without authentication. For version 6.0, valid credentials are required before the vulnerable code path can be reached.

Detection Methods for CVE-2025-6709

Indicators of Compromise

• Unexpected MongoDB server crashes with invariant failure messages in logs
• Repeated server restarts within short time windows indicating crash-restart cycles
• Authentication log entries showing unusual JSON payload patterns prior to crashes
• OIDC authentication attempts with malformed or unusual date values in request payloads

Detection Strategies

• Monitor MongoDB server logs for invariant failure messages and unexpected process terminations
• Implement network-level monitoring to detect anomalous JSON payload patterns targeting MongoDB ports
• Configure alerting on MongoDB process crashes and automatic restart events
• Review OIDC authentication logs for unusual date format patterns in incoming requests

Monitoring Recommendations

• Enable verbose logging for OIDC authentication events to capture suspicious payloads
• Implement process monitoring with automatic alerting when MongoDB services terminate unexpectedly
• Deploy network intrusion detection rules to identify malformed JSON date patterns targeting MongoDB
• Monitor system logs for repeated crash-restart cycles that may indicate active exploitation attempts

How to Mitigate CVE-2025-6709

Immediate Actions Required

• Upgrade MongoDB Server v7.0 to version 7.0.17 or later immediately
• Upgrade MongoDB Server v8.0 to version 8.0.5 or later immediately
• Upgrade MongoDB Server v6.0 to version 6.0.21 or later
• Restrict network access to MongoDB instances to trusted IP addresses and networks
• Consider temporarily disabling OIDC authentication if not critical until patches can be applied

Patch Information

MongoDB has released security patches addressing this vulnerability. Detailed information about the fix is available in the MongoDB Bug Report SERVER-106748. Organizations should prioritize upgrading to the patched versions:

• MongoDB Server v7.0.17+ for 7.0 series
• MongoDB Server v8.0.5+ for 8.0 series
• MongoDB Server v6.0.21+ for 6.0 series

Workarounds

• Implement firewall rules to restrict MongoDB access to trusted networks and IP addresses only
• If OIDC authentication is not required, consider switching to alternative authentication mechanisms
• Deploy a reverse proxy or application firewall capable of inspecting and filtering malformed JSON payloads
• Ensure MongoDB instances are not directly exposed to the public internet
• Implement rate limiting on authentication endpoints to slow potential exploitation attempts