CVE-2025-20359
📋 TL;DR
A buffer under-read vulnerability in Snort 3's HTTP decoder allows unauthenticated remote attackers to cause denial of service or information disclosure by sending crafted HTTP packets. This affects multiple Cisco products using Snort 3 for intrusion prevention. Attackers can crash the detection engine or potentially leak sensitive data from memory.
💻 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
Snort 3 detection engine crashes repeatedly, causing sustained denial of service for network security monitoring and potentially exposing sensitive memory contents including credentials or session data.
Likely Case
Intermittent Snort 3 restarts causing temporary DoS and possible information disclosure of non-critical memory contents.
If Mitigated
Minimal impact with proper network segmentation and monitoring; Snort 3 restarts automatically but may miss some traffic during restart.
🎯 Exploit Status
Exploitation requires sending crafted HTTP packets through an established connection that Snort 3 inspects. No authentication required.
🛠️ 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-mime-vulns-tTL8PgVH
Restart Required: Yes
Instructions:
1. Access Cisco Firepower Management Center or device CLI. 2. Download and install Snort 3 version 3.2.0.0 or later. 3. Apply the update to affected policies. 4. Restart Snort 3 services or reboot affected devices as required.
🔧 Temporary Workarounds
Disable Snort 3 HTTP inspection
allTemporarily disable HTTP inspection in Snort 3 policies to prevent exploitation while patching.
configure policy
edit affected_policy
set inspection http disable
commit
Implement network segmentation
allRestrict HTTP traffic to Snort 3 inspection points from untrusted sources.
🧯 If You Can't Patch
- Implement strict network ACLs to limit HTTP traffic to Snort 3 inspection points
- Monitor for Snort 3 process restarts and investigate any anomalies in HTTP traffic patterns
🔍 How to Verify
Check if Vulnerable:
Check Snort 3 version: 'show version' on CLI or navigate to Devices > Device Management > Version in FMCCheck Version:
show version | include SnortVerify Fix Applied:
Verify Snort 3 version is 3.2.0.0 or later and monitor for process stability📡 Detection & Monitoring
Log Indicators:
- Snort 3 process restarts
- Memory access violation errors in system logs
- Unexpected Snort 3 crashes
Network Indicators:
- Unusual HTTP header patterns
- MIME field manipulation attempts
- HTTP packets with malformed headers
SIEM Query:
source="firepower" AND ("Snort restart" OR "buffer under-read" OR "memory violation")