Quick answers
- Is CVE-2026-80303 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-80303 being exploited in the wild.
- How severe is CVE-2026-80303?
- Informational severity, published 6 November 2026.
- Which products and versions are affected?
- Avast Windows Filtering Platform.
- Is there a fix for CVE-2026-80303?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-80303 attacked?
- It is attacked over the network or with local access, in an operating system.
- Am I affected by CVE-2026-80303?
- Check whether you run Avast Windows Filtering Platform. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
An integer underflow vulnerability exists in the WFP stream parser's length computation for packet fragment reassembly. The vulnerable code fails to validate input stream sizes against expected boundaries, causing the length calculation to underflow and wrap around to an extremely large value. This can be triggered remotely via malicious network traffic to filtered ports or locally via crafted data to the filtering interface, resulting in failed memory allocation or out-of-bounds buffer access that triggers a kernel panic.
Affected products
- Avast Windows Filtering Platform
Timeline
- 2026-11-06: disclosed