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

Official 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.

Affected products (as reported)

References

• Gen Digital Security Advisories vendor-advisory
• Avast: how to update Avast Antivirus or Avast One patch
• AVG: updating AVG AntiVirus patch
• Norton: keep your Norton device security up to date patch
• PrettyPrague public proof-of-concept exploit
• Finder's public disclosure announcement