CVE-2025-20183
📋 TL;DR
This vulnerability allows unauthenticated remote attackers to bypass the antivirus scanner on Cisco Secure Web Appliance by sending crafted HTTP range request headers. Affected organizations using Cisco AsyncOS Software with policy-based AVC implementations could have malware downloaded onto endpoints undetected.
💻 Affected Systems
- Cisco Secure Web Appliance
📦 What is this software?
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⚠️ Risk & Real-World Impact
Worst Case
Malware delivery to endpoints leading to ransomware deployment, data exfiltration, or network compromise.
Likely Case
Targeted malware delivery to specific users or endpoints for credential theft or lateral movement.
If Mitigated
Limited impact if other security controls like endpoint protection, network segmentation, and user awareness are in place.
🎯 Exploit Status
Exploitation requires sending crafted HTTP range headers through the affected device
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Cisco advisory for specific fixed versions
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-swa-range-bypass-2BsEHYSu
Restart Required: Yes
Instructions:
1. Review Cisco advisory for affected versions 2. Download and apply appropriate patch 3. Restart Cisco Secure Web Appliance 4. Verify patch installation
🔧 Temporary Workarounds
Disable policy-based AVC
allTemporarily disable the vulnerable Application Visibility and Control feature
HTTP range header filtering
allImplement network filtering to block or inspect suspicious HTTP range headers
🧯 If You Can't Patch
- Implement network segmentation to isolate vulnerable appliances
- Deploy additional endpoint protection and monitoring solutions
🔍 How to Verify
Check if Vulnerable:
Check Cisco Secure Web Appliance version and AVC configuration against advisoryCheck Version:
Check device web interface or CLI for AsyncOS versionVerify Fix Applied:
Verify patch installation and test antivirus scanning functionality📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP range header patterns
- Antivirus scan bypass events
- Large file downloads without scanning
Network Indicators:
- HTTP requests with crafted range headers
- Unusual download patterns from external sources
SIEM Query:
http.request.header="Range" AND (http.request.header contains "bytes=0-1" OR http.request.header contains unusual_range_patterns)