Avast WFP stream parser integer underflow causes system crash

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-80303
StatePUBLISHED
AssignerGEN
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-06 16:18:59 UTC
Updated2026-11-06 16:18:59 UTC
DescriptionAn 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.

Risk And Classification

Problem Types: CWE-191 | CWE-248 | CWE-191 CWE-191: Integer Underflow (Wrap or Wraparound) | CWE-248 CWE-248: Uncaught Exception

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Gen Digital Avast Antivirus Avast One Avast Premium Security Avast Ultimate affected 26.7 custom Windows
CNA Gen Digital AVG Antivirus Free AVG Internet Security AVG Ultimate affected 26.7 custom Windows
CNA Gen Digital Norton Antivirus Plus Norton 360 Standard Norton 360 Deluxe Norton 360 Advanced affected 26.7 custom Windows

References

ReferenceSourceLinkTags
support.avg.com/SupportArticleView [email protected] support.avg.com
www.gendigital.com/us/en/contact-us/security-advisories [email protected] www.gendigital.com
support.avast.com/en-us/article/Update-Antivirus [email protected] support.avast.com
support.norton.com/sp/en/us/home/current/solutions/v20240108175512167 [email protected] support.norton.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Teng Zheng Wang by VulnGuard Labs (en)

Additional Advisory Data

Solutions

CNA: 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.

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