CISCO Security Advisory
Published Date: Not specified
CVE: CVE-2026-20218
Advisory Summary
🚨 ⚠️ Multiple Cisco Products: Snort 3 VBA Buffer Overflow DoS (Unauthenticated Remote Restart)
ℹ️ What’s happening?
Cisco disclosed a vulnerability in the Snort 3 Visual Basic for Applications (VBA) Decompression Engine used across multiple Cisco products. A remote attacker can trigger the Snort 3 Detection Engine to restart unexpectedly, producing a denial of service (DoS) condition. The issue is marked Medium.
🧨 Core cause
Improper range checking during decompression of user-controlled VBA data can lead to a stack data overflow, ultimately driving the DoS.
- An attacker sends crafted VBA data to the Snort 3 Detection Engine on a targeted device
- If successful, the engine overflows stack data and restarts (service disruption)
- ✅ Software updates have been released to remediate the vulnerability
- 🧰 A workaround is also available (details are provided in the advisory)
- Detection integrity risk: Restart loops can degrade visibility and incident response timelines
- Exposure assessment: Prioritize devices where Snort 3 with VBA decompression is enabled and reachable from untrusted networks
- Control check: Review whether any network path allows untrusted traffic to reach the Snort 3 Detection Engine parsing surface
🔐 Recommended next steps
1. Apply Cisco patches immediately for affected product/software versions
2. If immediate patching isn’t possible, implement the Cisco workaround
3. Validate Snort 3 deployment settings: confirm VBA usage/decompression exposure boundaries
4. Monitor for unexpected Detection Engine restarts and correlate with inbound traffic patterns
5. Track CVE-2026-20218 in your vulnerability management system and remediation SLAs
📌
-2026-20218
Reference: Vendor Advisory