CVE-2025-51495
📋 TL;DR
An integer overflow vulnerability in Mongoose's WebSocket component (versions 7.5 through 7.17) allows attackers to crash applications via specially crafted WebSocket requests. If downstream vendors integrate the component improperly, this could escalate to buffer overflow conditions. Systems using vulnerable Mongoose versions for WebSocket functionality are affected.
💻 Affected Systems
- Mongoose embedded web server/library
📦 What is this software?
Mongoose by Cesanta
⚠️ Risk & Real-World Impact
Worst Case
Buffer overflow leading to remote code execution if downstream vendors improperly integrate the vulnerable component, potentially compromising the entire system.
Likely Case
Denial of service through application crashes, disrupting WebSocket-dependent services and causing downtime.
If Mitigated
Limited to application crashes with minimal data loss if proper input validation and isolation controls are implemented.
🎯 Exploit Status
Exploitation requires sending malicious WebSocket requests; proof-of-concept code is publicly available in GitHub references.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 7.18 or later
Vendor Advisory: https://github.com/cesanta/mongoose/pull/3131
Restart Required: Yes
Instructions:
1. Update Mongoose to version 7.18 or later. 2. Rebuild and redeploy applications using the library. 3. Restart services to apply the fix.
🔧 Temporary Workarounds
Disable WebSocket functionality
allTemporarily disable WebSocket support in Mongoose configuration if not required.
Set MG_ENABLE_WEBSOCKET=0 in build configuration or disable via runtime settings
Network filtering
allBlock or filter WebSocket traffic at network boundaries using firewalls or WAFs.
Configure firewall rules to block WebSocket connections (typically port 80/443 with WebSocket headers)
🧯 If You Can't Patch
- Implement strict input validation for WebSocket requests to prevent malicious payloads.
- Isolate Mongoose instances in containers or sandboxes to limit crash impact.
🔍 How to Verify
Check if Vulnerable:
Check Mongoose version in source code or compiled binaries; versions 7.5-7.17 are vulnerable.Check Version:
Check version in source code (e.g., MG_VERSION macro) or use library's version API if available.Verify Fix Applied:
Confirm Mongoose version is 7.18 or later and test WebSocket functionality for stability.📡 Detection & Monitoring
Log Indicators:
- Unexpected application crashes or restarts
- WebSocket connection errors with malformed data
Network Indicators:
- Unusual WebSocket traffic patterns or large payloads
SIEM Query:
Search for logs containing 'mongoose crash', 'websocket error', or abnormal termination events.