CVE-2026-20027
📋 TL;DR
A buffer out-of-bounds read vulnerability in Cisco Snort 3's DCE/RPC request processing allows unauthenticated remote attackers to cause information disclosure or service interruption. This affects multiple Cisco products using Snort 3 for packet inspection. Attackers can exploit this by sending crafted DCE/RPC requests through monitored connections.
💻 Affected Systems
- Cisco Firepower Threat Defense
- Cisco Secure Firewall Management Center
- Cisco Secure Firewall
- Other Cisco products using Snort 3
⚠️ 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
Sensitive information leakage from Snort 3 data streams and denial of service through repeated Snort 3 restarts, potentially bypassing security monitoring.
Likely Case
Information disclosure of packet inspection data and intermittent service disruption of Snort 3 detection capabilities.
If Mitigated
Limited impact with proper network segmentation and access controls preventing unauthorized DCE/RPC traffic to affected systems.
🎯 Exploit Status
Requires ability to send DCE/RPC requests through established connections that Snort 3 inspects.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Snort 3 version 3.2.0.0 or later
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort3-dcerpc-vulns-J9HNF4tH
Restart Required: Yes
Instructions:
1. Review Cisco advisory for specific product updates. 2. Apply recommended software updates for affected Cisco products. 3. Restart affected services or devices as required.
🔧 Temporary Workarounds
Disable DCE/RPC inspection
allTemporarily disable DCE/RPC inspection in Snort 3 policies if not required for security monitoring.
Configure via Cisco management interface - no universal CLI command
Network segmentation
allRestrict DCE/RPC traffic to trusted sources only using firewall rules.
access-list deny tcp any any eq 135
access-list deny tcp any any eq 445
access-list deny udp any any eq 135
access-list deny udp any any eq 445
🧯 If You Can't Patch
- Implement strict network access controls to limit DCE/RPC traffic to affected systems.
- Monitor for unusual DCE/RPC traffic patterns and Snort 3 restart events.
🔍 How to Verify
Check if Vulnerable:
Check Snort 3 version via Cisco device CLI: 'show version' or management interface.Check Version:
show version | include SnortVerify Fix Applied:
Confirm Snort 3 version is 3.2.0.0 or later and verify DCE/RPC inspection functions normally.📡 Detection & Monitoring
Log Indicators:
- Snort 3 process restarts
- Buffer read errors in Snort logs
- Unusual DCE/RPC traffic volume
Network Indicators:
- Spike in DCE/RPC traffic to monitored systems
- TCP/UDP ports 135/445 traffic patterns
SIEM Query:
source="snort" AND ("restart" OR "buffer" OR "out of bounds")