---
id: "CVE-2026-20218"
kind: "vulnerability"
aliases: ["CVE-2026-20218"]
title: "Cisco Snort 3: crafted VBA data crashes the detection engine"
severity: "medium"
cvss: 5.8
epss: 0.00416
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["cisco", "infrastructure", "network-security", "snort-3"]
not_affected_if: ["no-snort-3"]
published_at: "2026-10-21T17:18:27+00:00"
first_seen_at: "2026-10-23T21:57:29+00:00"
updated_at: "2026-10-25T04:10:02+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-20218", "first_seen_at": "2026-10-23T21:57:29+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-20218", "first_seen_at": "2026-10-24T13:15:54+00:00"}]
---

# Cisco Snort 3: crafted VBA data crashes the detection engine

Snort 3's VBA decompression engine in multiple Cisco products does not check ranges properly when decompressing user-controlled VBA data. A remote, unauthenticated attacker can send crafted traffic that restarts the Snort 3 Detection Engine, causing denial of service.

_Summary, check and fix written by a model from the sources; labelled as such._

## Timeline

- 2026-10-23T21:57:29+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-20218
- 2026-10-24T13:15:54+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-20218

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_