CVE-2026-20056
📋 TL;DR
This vulnerability allows unauthenticated remote attackers to bypass anti-malware scanning on Cisco Secure Web Appliances by sending specially crafted archive files. Affected organizations using vulnerable Cisco AsyncOS versions could have malware downloaded to end-user workstations, though user interaction is required for execution.
💻 Affected Systems
- Cisco Secure Web Appliance (formerly Web Security Appliance)
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Malicious actors deliver ransomware or other malware to multiple endpoints, leading to data encryption, exfiltration, or system compromise after users extract and execute the files.
Likely Case
Targeted attackers bypass web filtering to deliver malware payloads to specific users, potentially leading to credential theft or initial access for further attacks.
If Mitigated
Even if malware is downloaded, endpoint protection, user awareness, and proper extraction controls prevent execution and limit impact.
🎯 Exploit Status
Exploitation requires sending crafted archive files through the appliance; no authentication needed. Attackers need to convince users to extract and execute downloaded files.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Cisco advisory for specific fixed releases
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-wsa-archive-bypass-Scx2e8zF
Restart Required: Yes
Instructions:
1. Review Cisco advisory for affected versions. 2. Download and apply the appropriate patch from Cisco. 3. Restart the Cisco Secure Web Appliance as required. 4. Verify the update was successful.
🔧 Temporary Workarounds
Block suspicious archive file types
allConfigure web filtering policies to block or warn on archive file downloads that could be crafted to exploit this vulnerability.
Enforce endpoint protection
allEnsure all endpoints have updated anti-malware software that can detect malicious archives even if web filtering is bypassed.
🧯 If You Can't Patch
- Implement network monitoring for unusual archive file downloads through the web appliance
- Enhance user awareness training about risks of opening unexpected archive files
🔍 How to Verify
Check if Vulnerable:
Check Cisco Secure Web Appliance version against affected versions listed in the Cisco advisory.Check Version:
Log into Cisco Secure Web Appliance CLI or web interface and check system version information.Verify Fix Applied:
Confirm appliance version matches or exceeds the patched version specified in Cisco advisory.📡 Detection & Monitoring
Log Indicators:
- Unusual archive file download patterns in web proxy logs
- Multiple failed malware scan attempts for archive files
Network Indicators:
- Increased archive file downloads from suspicious sources
- Archive files with unusual headers or structures
SIEM Query:
source="cisco_wsa" AND (file_type="zip" OR file_type="rar" OR file_type="7z") AND action="allowed" AND malware_scan="bypassed"