---
id: "CVE-2026-80303"
page: "https://infrastack.ai/live/CVE-2026-80303"
kind: "vulnerability"
aliases: ["CVE-2026-80303"]
title: "Avast Windows WFP stream parser: integer underflow crashes Windows"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "other"
products: []
ecosystems: []
tags: ["avast", "kernel-driver", "other", "windows"]
not_affected_if: ["no-avast-installed"]
published_at: "2026-11-06T16:18:59+00:00"
first_seen_at: "2026-11-06T16:42:42+00:00"
updated_at: "2026-11-06T16:44:55+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-80303", "first_seen_at": "2026-11-06T16:42:42+00:00"}]
exploit_sources: []
---

# Avast Windows WFP stream parser: integer underflow crashes Windows

Link for people: https://infrastack.ai/live/CVE-2026-80303 (this .md is for agents)

An integer underflow in the Avast Windows Filtering Platform stream parser lets crafted network traffic or local input wrap a length value. The result is a kernel panic that crashes the Windows machine.

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

## How to check

- Check whether Avast's Windows Filtering Platform callout driver is installed on the machine
- Confirm the installed Avast product version against the vendor's advisory, which the sources do not name

## Timeline

- 2026-11-06T16:42:42+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-80303

## From the sources

An integer underflow vulnerability in the Avast Windows Filtering Platform (WFP) stream parser on Windows allows denial of service by causing a system crash.



The WFP callout driver processes network stream data and computes length values for packet fragment reassembly. The length calculation does not properly validate input stream sizes against expected boundaries. When processing specially crafted input, the length computation underflows, resulting in allocation or buffer access with an extremely large wrapped-around size value.



The underflow can be triggered remotely via network traffic destined for the filtered port, or locally via crafted data provided to the filtering interface. The resulting memory allocation failure or out-of-bounds access causes a kernel panic and system crash.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_