---
id: CVE-2026-80303
title: Avast WFP stream parser integer underflow causes system crash
summary: >-
  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 val…
severity: none
cwe:
  - CWE-191
  - CWE-248
vendor: Gen Digital
product: 'Avast Antivirus, Avast One, Avast Premium Security, Avast Ultimate'
affected:
  - avast_antivirus_avast_one_avast_premium_security_avast_ultimate < 26.7
  - avg_antivirus_free_avg_internet_security_avg_ultimate < 26.7
  - >-
    norton_antivirus_plus_norton_360_standard_norton_360_deluxe_norton_360_advanced
    < 26.7
published: '2026-11-06'
updated: '2026-11-06'
sourceUpdated: '2026-11-06T15:59:24.348Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-80303'
references:
  - url: 'https://www.gendigital.com/us/en/contact-us/security-advisories/'
    label: Gen Digital Security Advisories
  - url: 'https://support.avast.com/en-us/article/Update-Antivirus'
    label: 'Avast: how to update Avast Antivirus or Avast One'
  - url: >-
      https://support.avg.com/SupportArticleView?l=en&urlname=Update-AVG-Antivirus
    label: 'AVG: updating AVG AntiVirus'
  - url: >-
      https://support.norton.com/sp/en/us/home/current/solutions/v20240108175512167
    label: 'Norton: keep your Norton device security up to date'
tags:
  - cve.org
ingestedAt: '2026-11-06T16:57:43.382Z'
epss: 0.00157
epssPercentile: 0.04845
---

## Overview

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.

## Affected

- `avast_antivirus_avast_one_avast_premium_security_avast_ultimate < 26.7`
- `avg_antivirus_free_avg_internet_security_avg_ultimate < 26.7`
- `norton_antivirus_plus_norton_360_standard_norton_360_deluxe_norton_360_advanced < 26.7`

## Remediation

Gen Digital has released a fix in Avast, AVG, and Norton version 26.7 and later. The fix adds input validation to the WFP stream parser length computation to detect and reject underflow conditions before they can result in memory allocation or access with invalid sizes.



Upgrade to version 26.7 or later to remediate this issue.