CVE-2025-20263
📋 TL;DR
An unauthenticated remote attacker can exploit a buffer overflow vulnerability in Cisco ASA and FTD web services by sending a crafted HTTP request. This causes the system to reload, resulting in denial of service. Organizations using affected Cisco firewall products with web services enabled are at risk.
💻 Affected Systems
- Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
- Cisco Secure Firewall Threat Defense (FTD) Software
⚠️ 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
Complete system outage with extended downtime, potential for remote code execution if buffer overflow can be manipulated beyond DoS
Likely Case
Service disruption causing firewall reload and temporary network interruption
If Mitigated
Minimal impact if web services interface is disabled or properly firewalled
🎯 Exploit Status
Crafting HTTP requests to trigger buffer overflow is relatively straightforward
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to Cisco Security Advisory for specific fixed versions
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-buffer-overflow-PyRUhWBC
Restart Required: Yes
Instructions:
1. Review Cisco advisory for affected versions 2. Download and apply appropriate patch 3. Schedule maintenance window for firewall restart 4. Verify patch application
🔧 Temporary Workarounds
Disable Web Services Interface
allDisable the vulnerable web services interface if not required
no http server enable
no http secure-server enable
Restrict Access to Web Services
allLimit access to web services interface using ACLs
http access-class ACL-NAME
🧯 If You Can't Patch
- Implement strict network segmentation to limit access to web services interface
- Deploy intrusion prevention systems with signatures for buffer overflow attacks
🔍 How to Verify
Check if Vulnerable:
Check ASA/FTD version against affected versions in Cisco advisoryCheck Version:
show version | include VersionVerify Fix Applied:
Verify version after patch and test web services functionality📡 Detection & Monitoring
Log Indicators:
- Unexpected system reloads
- Web service crashes
- Memory allocation errors in system logs
Network Indicators:
- Unusual HTTP requests to firewall management interface
- Traffic patterns indicating DoS attempts
SIEM Query:
source="asa" OR source="ftd" AND (event_type="crash" OR event_type="reload" OR message="*buffer*" OR message="*overflow*")