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Fencer Intel
medium 6.2

CVE-2026-80303 json

Avast WFP stream parser integer underflow causes system crash

published 5d ago modified yesterday also EUVD-2026-118328

cvss
6.2
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 2%
public exploits
0
none known

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 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.

Patch / fix

  • Gen Digital Avast Antivirus, Avast One, Avast Premium Security, Avast Ultimate 26.7
  • Gen Digital AVG Antivirus Free, AVG Internet Security, AVG Ultimate 26.7
  • Gen Digital Norton Antivirus Plus, Norton 360 Standard, Norton 360 Deluxe, Norton 360 Advanced 26.7

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
yesterday

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CISA ADP 3.1 6.2 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 3.1 6.2 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Gen Digital Avast Antivirus, Avast One, Avast Premium Security, Avast Ultimate
  • Gen Digital AVG Antivirus Free, AVG Internet Security, AVG Ultimate
  • Gen Digital Norton Antivirus Plus, Norton 360 Standard, Norton 360 Deluxe, Norton 360 Advanced

Classification

Weakness
  • CWE-191 Integer Underflow (Wrap or Wraparound)
  • CWE-248 Uncaught Exception

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.