CVE-2026-82964

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.

Affected Software

VendorProductVersion RangeStatus
Gen DigitalAvast Free Antivirus, Avast One, Avast Premium Security, Avast Ultimate, Avast Business Security0 < 26.8affected
Gen DigitalAVG Antivirus Free, AVG Internet Security, AVG Ultimate0 < 26.8affected
Gen DigitalNorton Antivirus Plus, Norton 360 Standard, Norton 360 Deluxe, Norton 360 Advanced0 < 26.8affected

Weaknesses

  • CWE-281: CWE-281: Improper Preservation of Permissions
  • CWE-653: CWE-653: Improper Isolation or Compartmentalization
  • CWE-862: CWE-862: Missing Authorization

Workarounds

Applying the driver micro-update described under Solution is the only complete remediation.

Where that update cannot be applied, Gen Digital ships detection for exploitation attempts against this issue, so keeping product virus definitions current provides detection of the publicly released proof-of-concept. Detection of a known proof-of-concept is not equivalent to the code fix and does not prevent variants.

Where the sandbox feature is not required, disabling it removes exposure to this attack path.

References