CVE-2026-80303
Avast WFP stream parser integer underflow causes system crash
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.
Exploit likelihood
What each source reports
CVE List No score
Avast WFP stream parser integer underflow causes system crash
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.
- Record
CVE-2026-80303- Weakness
- CWE-191, CWE-248
- Updated
- 2026-11-06
EUVDEUVD-2026-118328 No score
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.
- Record
EUVD-2026-118328- Updated
- 2026-11-06
GitHub AdvisoriesGHSA-2q9r-4cp6-374g No score
An integer underflow vulnerability in the Avast Windows Filtering Platform (WFP) stream parser on...
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.
- Record
GHSA-2q9r-4cp6-374g- Weakness
- CWE-191
- Updated
- 2026-11-06
NVD No score
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.
- Record
CVE-2026-80303- Weakness
- CWE-191, CWE-248
- Updated
- 2026-11-06
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| published | EUVD | |
| published | EUVD | |
| aliases, references | GitHub Advisories, NVD | |
| cwes, references, title | CVE List | |
| first indexed | EUVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-80303 is a vulnerability with no CVSS score yet in Gen Digital Avast Antivirus, Avast One, Avast Premium Security, Avast Ultimate, published November 6, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.16%, the 4th percentile. No source names a fixed version.
References
gendigital.com/us/en/contact-us/security-advisories
support.avast.com/en-us/article/Update-Antivirus
support.avg.com/SupportArticleView?l=en&urlname=Update-AVG-Antivirus
support.norton.com/sp/en/us/home/current/solutions/v20240108175512167
nvd.nist.gov/vuln/detail/CVE-2026-80303
github.com/advisories/GHSA-2q9r-4cp6-374g