CISCO Security Advisory
Published Date: Not specified
CVE: CVE-2026-20011
Advisory Summary
🚨 Multiple Cisco Products — Snort 3 SMTP MIME DoS Vulnerability (CVE-2026-20011)
⚠️ What happened?
Cisco reports a vulnerability in the Snort 3 SMTP MIME Decoder that can be triggered by an unauthenticated remote attacker. The issue is caused by insufficient error checking while parsing MIME fields within SMTP headers.
- An attacker sends crafted SMTP packets over an established connection
- Snort 3 processes the malicious MIME content
- Result: the Snort 3 Detection Engine can restart, creating a Denial of Service (DoS) condition
- Security Impact Rating: Medium
- Primary risk: Loss of detection/visibility due to repeated engine restarts (operational degradation that can be exploited during active attacks)
🛠️ Cisco guidance / remediation
✅ Updates are available that address the flaw.
❌ No workarounds are provided for this vulnerability—so patching (or equivalent mitigation via vendor guidance) is the practical path.
- Prioritize patching for Snort 3 deployments exposed to SMTP traffic or used for email-based inspection/monitoring.
- Validate whether your Snort 3 sensors/engines are reachable by adversaries that can establish SMTP sessions.
- Review operational controls for detection continuity (e.g., monitoring for unexpected Snort restarts, alerting on engine health).
🔗
-2026-20011
Reference: Vendor Advisory