CVE-2023-49550 – A denial-of-service vulnerability in Cesanta mj... (How to Fix)

Q: What is the severity of CVE-2023-49550?

CVE-2023-49550 has a CVSS score of 7.5 (HIGH). A denial-of-service vulnerability in Cesanta mjs 2.20.0 allows remote attackers to crash applications using this embedded JavaScript engine via a specific component. This affects any system running vulnerable versions of mjs, particularly IoT devices and embedded systems that incorporate this engine.

📋 TL;DR

A denial-of-service vulnerability in Cesanta mjs 2.20.0 allows remote attackers to crash applications using this embedded JavaScript engine via a specific component. This affects any system running vulnerable versions of mjs, particularly IoT devices and embedded systems that incorporate this engine.

💻 Affected Systems

Products:

Cesanta mjs

Versions: 2.20.0

Operating Systems: All platforms running mjs

Default Config Vulnerable: ⚠️ Yes

Notes: Any application or device using the vulnerable mjs version is affected regardless of configuration.

📦 What is this software?

Mjs by Cesanta

View all CVEs affecting Mjs →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete service disruption with application crashes leading to unavailability of affected systems or devices.

🟠

Likely Case

Application instability and crashes causing intermittent service interruptions.

🟢

If Mitigated

Minimal impact with proper network segmentation and monitoring in place.

🌐 Internet-Facing: HIGH - Remote attackers can trigger the vulnerability without authentication.

🏢 Internal Only: MEDIUM - Internal attackers could still exploit this, but requires network access.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

The GitHub issue contains technical details that could facilitate exploitation.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Check latest mjs releases after 2.20.0

Vendor Advisory: https://github.com/cesanta/mjs/issues/252

Restart Required: Yes

Instructions:

1. Check current mjs version. 2. Update to latest patched version from official repository. 3. Rebuild and redeploy affected applications. 4. Restart services using mjs.

🔧 Temporary Workarounds

Network segmentation

all

Restrict network access to systems using mjs to trusted sources only

Input validation

all

Implement strict input validation for data processed by mjs engine

🧯 If You Can't Patch

Implement strict network access controls to limit exposure
Deploy monitoring and alerting for application crashes or abnormal behavior

🔍 How to Verify

Check if Vulnerable:

Check if mjs version 2.20.0 is installed in your system or applications

Check Version:

Check application dependencies or build configuration for mjs version

Verify Fix Applied:

Verify mjs version is updated to a release after 2.20.0 and test application stability

📡 Detection & Monitoring

Log Indicators:

Application crashes
Abnormal termination of mjs processes
Memory error logs

Network Indicators:

Unexpected traffic patterns to mjs endpoints

SIEM Query:

search for process termination events related to mjs or containing 'mjs' in process name

📊 Metadata

CVE ID: CVE-2023-49550

CVSS v3 Score: 7.5 (HIGH)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE: CWE-400

Published: January 2, 2024

Last Updated: May 16, 2025

🔗 References

https://github.com/cesanta/mjs/issues/252 Exploit,Issue Tracking,Vendor Advisory
https://github.com/cesanta/mjs/issues/252 Exploit,Issue Tracking,Vendor Advisory

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🔗 Related Vulnerabilities

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