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Fencer Vulns
high 8.8

CVE-2026-82964 json

Avast sandbox privilege escalation via unpreserved DACLs on virtualized files in aswSnx.sys

published 2026-09-16 54 d ago modified 2026-09-17 52 d ago also EUVD-2026-80773

cvss
8.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 4%
public exploits
0
none known

Summary

Improper preservation of permissions in the Avast sandbox minifilter driver (aswSnx.sys) on Windows allows a local, low-privileged attacker executing inside the sandbox to escape file isolation and escalate to SYSTEM.

When the sandbox virtualizes a file it copies the original security descriptor, but the driver opened the virtualization target object with GENERIC_WRITE and FILE_WRITE_ATTRIBUTES only, omitting WRITE_DAC. Every attempt to apply the original DACL therefore failed, and the failure was discarded silently, leaving virtualized copies of sensitive files with permissive permissions. Because the IRP_MJ_CREATE callback additionally did not strip WRITE_DAC for sensitive directories, a sandboxed process could rewrite the security descriptor of a virtualized object, read the virtualized copy of the SAM database, extract local NTLM password hashes and execute code as SYSTEM.

The absence of an IRP_MJ_SET_SECURITY callback in the driver's operation registration table is a related defense-in-depth gap, but it is not the control that prevents this attack.

Patch / fix

  • Gen Digital Avast Free Antivirus, Avast One, Avast Premium Security, Avast Ultimate, Avast Business Security 26.8
  • Gen Digital AVG Antivirus Free, AVG Internet Security, AVG Ultimate 26.8
  • Gen Digital Norton Antivirus Plus, Norton 360 Standard, Norton 360 Deluxe, Norton 360 Advanced 26.8

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
total
Assessed
52 d ago

Exploit prediction

0.16% chance of exploitation in the next 30 days, higher than 4% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/MSNightmare/PrettyPrague referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 8.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Affected products

  • Gen Digital Avast Free Antivirus, Avast One, Avast Premium Security, Avast Ultimate, Avast Business Security
  • 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-281 Improper Preservation of Permissions
  • CWE-653 Improper Isolation or Compartmentalization
  • CWE-862 Missing Authorization

References

Sources

Fencer Vulns 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.