CVE-2020-26574
📋 TL;DR
CVE-2020-26574 is a stored cross-site scripting (XSS) vulnerability in Leostream Connection Broker 8.2.x that allows unauthenticated attackers to inject malicious JavaScript via User-Agent headers. This can lead to remote code execution as root when admins view the malicious content. Only affects unsupported versions of Leostream Connection Broker.
💻 Affected Systems
- Leostream Connection Broker
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with root-level remote code execution, allowing attacker to install backdoors, steal data, or pivot to other systems.
Likely Case
Administrative account compromise leading to session hijacking, data theft, and potential privilege escalation within the Leostream environment.
If Mitigated
Limited to XSS payload execution in admin browser context without successful RCE due to additional security controls.
🎯 Exploit Status
Public exploit details available showing XSS to RCE chain. Attack requires admin to view malicious content.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: N/A
Vendor Advisory: https://www.leostream.com/resources/product-lifecycle/
Restart Required: No
Instructions:
No official patch available. Upgrade to supported version or implement workarounds.
🔧 Temporary Workarounds
Input Validation for User-Agent Headers
allImplement strict input validation and sanitization for User-Agent headers in webquery.pl
Modify webquery.pl to sanitize User-Agent input using HTML entity encoding
Content Security Policy
allImplement Content Security Policy headers to restrict script execution
Add 'Content-Security-Policy: default-src 'self'' to HTTP headers
🧯 If You Can't Patch
- Isolate Leostream instances behind network segmentation with strict firewall rules
- Implement web application firewall (WAF) with XSS protection rules
🔍 How to Verify
Check if Vulnerable:
Check if Leostream version is 8.2.x and test for XSS via User-Agent header injection in webquery.plCheck Version:
Check Leostream admin interface or configuration files for version informationVerify Fix Applied:
Test that User-Agent header input is properly sanitized and no script execution occurs📡 Detection & Monitoring
Log Indicators:
- Unusual User-Agent strings in web server logs
- Multiple requests to webquery.pl with JavaScript patterns
Network Indicators:
- HTTP requests with malicious JavaScript in User-Agent headers
- Unexpected outbound connections from Leostream server
SIEM Query:
source="leostream_logs" AND (User-Agent CONTAINS "<script>" OR User-Agent CONTAINS "javascript:")