As reported by SecurityAffairs, security researcher Chaotic Eclipse (aka INFINITE NIGHTMARE) has publicly released PrettyPrague, a proof-of-concept exploit targeting an unpatched privilege escalation vulnerability in GenDigital's Avast Antivirus. The PoC reportedly abuses a flaw in the Avast Sandbox component to dump the Windows SAM database and spawn a full SYSTEM-level shell — and works against fully patched Avast Antivirus running on Windows 11 25H2. No CVE has been assigned and no patch exists at the time of writing.

Security Impact: As reported by SecurityAffairs, security researcher Chaotic Eclipse (aka INFINITE NIGHTMARE) has publicly released PrettyPrague, a proof-of-concept exploit targeting an unpatched privilege escalation vulnerability in GenDigital's Avast Antivirus.

This is not an isolated event. Chaotic Eclipse has a documented track record of releasing weaponizable PoCs for endpoint security products, including the recent HardBreacher exploit targeting Kaspersky Endpoint Security and the Undefend and RedSun Defender zero-days targeting Microsoft Defender. Some of these prior releases have subsequently been exploited in the wild, which elevates the urgency of this disclosure considerably.

Why This Matters

Antivirus and EDR products run at the highest privilege levels on endpoints — often as kernel drivers or SYSTEM-level services. This architecture makes them attractive targets for privilege escalation. When the very tool designed to protect a system becomes the vector for full SYSTEM compromise, defenders face a paradox: the security product itself becomes the attack surface.

The SAM database dump capability is particularly dangerous. The Security Account Manager database contains hashed credentials for all local accounts. With SYSTEM-level access, an attacker can exfiltrate these hashes and conduct offline cracking or pass-the-hash attacks to move laterally across the domain.

Vulnerability Summary

FieldDetails
ProductGenDigital Avast Antivirus (all versions reportedly affected)
ComponentAvast Sandbox
Vulnerability TypeLocal Privilege Escalation
ImpactSAM database dump; SYSTEM-level shell
CVENot yet assigned
CVSSNot yet scored (assessed as High to Critical pending vendor confirmation)
Patch AvailableNo — zero-day, unpatched at time of disclosure
Active ExploitationPoC publicly released; in-the-wild exploitation not yet confirmed
Potentially AffectedAvast, and possibly AVG and Norton (other GenDigital products) — unconfirmed
Tested EnvironmentFully patched Avast Antivirus on Windows 11 25H2

Who Is at Risk

Who Is at Risk
Consumer and SMB environments relying on Avast Free or Premium as their primary endpoint protection — these users rarely have layered defenses.
Organizations using AVG or Norton products, if the Avast Sandbox component is shared across GenDigital's product line as the researcher suspects.
Managed environments where Avast is deployed via group policy or MDM — a single compromised low-privilege user could escalate to SYSTEM and pivot.

Shield53 Recommendations

Immediate Actions

  • Restrict Avast Sandbox exposure: If your environment permits, consider temporarily disabling the Avast Sandbox feature until a patch is issued. Evaluate the trade-off against your threat model.
  • Deploy application control or EDR: Use a secondary, vendor-diverse EDR solution to detect SAM database access patterns (e.g., reg save, Volume Shadow Copy access to SAM) and SYSTEM shell spawning from unusual parent processes.
  • Enable Windows Defender Credential Guard: Virtualization-based security for credentials can mitigate SAM dump impact by protecting secrets even when an attacker reaches SYSTEM.
  • Hunt for indicators: Monitor for processes named after the PoC, unexpected child processes of Avast Sandbox components, and any access to SAM or SYSTEM registry hives via reg save, ntdsutil, or taskmgr.
  • Reduce local admin sprawl: Limit the number of local admin accounts to reduce the value of a SAM dump. Enforce LAPS for randomized, rotated local admin passwords.
  • Monitor GenDigital advisories: Track GenDigital's security advisory pages for Avast, AVG, and Norton for patch releases. Apply patches immediately upon availability.

Detection Guidance

Defenders should build detection rules around the behavioral chain: a low-privilege process interacting with Avast Sandbox components, followed by registry hive access to SAM/SYSTEM, or spawning of a shell with SYSTEM integrity level. Sysmon Event ID 10 (ProcessAccess) targeting lsass.exe and Event ID 4663 (object access to SAM registry keys) are strong starting points.

The release of PrettyPrague underscores a recurring lesson: endpoint security tools that operate at kernel or SYSTEM level must be held to the highest secure development standards. Each new PoC in this category is a reminder that your security stack is also your attack surface.

Shield53 will continue monitoring this developing situation and will update guidance as GenDigital responds and CVE details emerge.