CVE-2020-19693
📋 TL;DR
This vulnerability in Espruino allows attackers to execute arbitrary code by exploiting the oldFunc parameter in the jswrap_object.c:jswrap_function_replacewith endpoint. It affects Espruino firmware versions containing the vulnerable code. This is a critical remote code execution vulnerability with CVSS 9.8.
💻 Affected Systems
- Espruino
📦 What is this software?
Espruino by Espruino
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attacker to execute arbitrary code, potentially taking full control of the device running Espruino.
Likely Case
Remote code execution leading to device compromise, data theft, or use as part of a botnet.
If Mitigated
Limited impact if proper network segmentation and access controls prevent exploitation attempts.
🎯 Exploit Status
The GitHub issue contains technical details that could be used to develop exploits.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after the fix for commit 6ea4c0a
Vendor Advisory: https://github.com/espruino/Espruino/issues/1684
Restart Required: Yes
Instructions:
1. Update Espruino to the latest version. 2. Rebuild and reflash firmware on affected devices. 3. Verify the fix is applied.
🔧 Temporary Workarounds
Network Segmentation
allIsolate Espruino devices from untrusted networks and internet access.
Access Control
allImplement strict network access controls to limit who can communicate with Espruino devices.
🧯 If You Can't Patch
- Isolate affected devices in a separate VLAN with strict firewall rules
- Monitor network traffic to/from Espruino devices for exploitation attempts
🔍 How to Verify
Check if Vulnerable:
Check Espruino version and compare against vulnerable commit 6ea4c0a. Review device firmware version.Check Version:
Check Espruino firmware version through device interface or consoleVerify Fix Applied:
Verify Espruino has been updated to a version that includes the fix for this vulnerability.📡 Detection & Monitoring
Log Indicators:
- Unusual function calls to jswrap_function_replacewith endpoint
- Abnormal process execution patterns
Network Indicators:
- Suspicious network traffic to Espruino devices on unusual ports
- Unexpected outbound connections from Espruino devices
SIEM Query:
Search for network connections to Espruino devices followed by abnormal system behavior