CVE-2026-20218

Cisco Secure Firewall Threat Defense Snort 3 Visual Basic for Applications Buffer Overflow Denial of Service Vulnerability

MEDIUM

5.8

CVSS Score

Published: October 21, 2026 at 04:12 PM UTC

Updated: October 22, 2026 at 07:17 PM UTC

3 products affected across 1 vendorSecure Firewall Threat DefenseUnified Threat Defense Snort Intrusion Prevention System EngineCisco Open Source Snort3

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Severity

MEDIUM5.8

Exploit prediction

EPSS 0.6%

SSVC

No known exploit

Description

A vulnerability in the Snort 3 Visual Basic for Applications (VBA) Decompression Engine of multiple Cisco products could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to improper range checking when Snort 3 decompresses VBA data, which is user controlled. An attacker could exploit this vulnerability by sending crafted VBA data to the Snort 3 Detection Engine of a targeted device. A successful exploit could allow the attacker to cause an overflow of stack data, which could result in a DoS condition.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Cisco Open Source Snort3 · Cisco

90%

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