Avast and AVG Antivirus for Windows were susceptible to a Time-of-check/Time-of-use (TOCTOU) vulnerability in the Quarantine process, leading to arbitrary file/directory deletion. The issue was fixed with Avast and AVG Antivirus version 22.11 and virus definitions from 14 February 2023 or later.

Avast Free Antivirus AvastSvc Link Following Local Privilege Escalation Vulnerability

Avast Free Antivirus AvastSvc Link Following Local Privilege Escalation Vulnerability. This vulnerability allows local attackers to escalate privileges on affected installations of Avast Free Antivirus. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the Avast Service. By creating a symbolic link, an attacker can abuse the service to delete a folder. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of SYSTEM. Was ZDI-CAN-23731.

Avast Free Antivirus AvastSvc Link Following Local Privilege Escalation Vulnerability

Avast Free Antivirus AvastSvc Link Following Local Privilege Escalation Vulnerability. This vulnerability allows local attackers to escalate privileges on affected installations of Avast Free Antivirus. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the Avast Service. By creating a symbolic link, an attacker can abuse the service to delete a folder. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of SYSTEM. Was ZDI-CAN-22963.

Avast Free Antivirus AvastSvc Link Following Local Privilege Escalation Vulnerability

Avast Free Antivirus AvastSvc Link Following Local Privilege Escalation Vulnerability. This vulnerability allows local attackers to escalate privileges on affected installations of Avast Free Antivirus. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the Avast Service. By creating a symbolic link, an attacker can abuse the service to delete a file. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of SYSTEM. Was ZDI-CAN-22272.

Avast Free Antivirus Link Following Denial-of-Service Vulnerability

Avast Free Antivirus Link Following Denial-of-Service Vulnerability. This vulnerability allows local attackers to create a denial-of-service condition on affected installations of Avast Free Antivirus. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the Avast Service. By creating a symbolic link, an attacker can abuse the service to create a folder. An attacker can leverage this vulnerability to create a denial-of-service condition on the system. Was ZDI-CAN-22806.

Avast Cleanup Premium Link Following Local Privilege Escalation Vulnerability

Avast Cleanup Premium Link Following Local Privilege Escalation Vulnerability. This vulnerability allows local attackers to escalate privileges on affected installations of Avast Cleanup Premium. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the Avast Cleanup Service. By creating a symbolic link, an attacker can abuse the service to delete a file. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of SYSTEM. Was ZDI-CAN-22892.

Avast Cleanup Premium Link Following Local Privilege Escalation Vulnerability

Avast Cleanup Premium Link Following Local Privilege Escalation Vulnerability. This vulnerability allows local attackers to escalate privileges on affected installations of Avast Cleanup Premium. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the Avast Cleanup Service. By creating a symbolic link, an attacker can abuse the service to delete a file. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of SYSTEM. Was ZDI-CAN-22893.

Avast Cleanup Premium Link Following Local Privilege Escalation Vulnerability

Avast Cleanup Premium Link Following Local Privilege Escalation Vulnerability. This vulnerability allows local attackers to escalate privileges on affected installations of Avast Cleanup Premium. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the Avast Cleanup Service. By creating a symbolic link, an attacker can abuse the service to delete a file. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of SYSTEM. Was ZDI-CAN-22894.

Elevation of Privelage via symlinked file in Avast Antivirus

A sym-linked file accessed via the repair function in Avast Antivirus <24.2 on Windows may allow user to elevate privilege to delete arbitrary files or run processes as NT AUTHORITY\SYSTEM. The vulnerability exists within the "Repair" (settings -> troubleshooting -> repair) feature, which attempts to delete a file in the current user's AppData directory as NT AUTHORITY\SYSTEM. A low-privileged user can make a pseudo-symlink and a junction folder and point to a file on the system. This can provide a low-privileged user an Elevation of Privilege to win a race-condition which will re-create the system files and make Windows callback to a specially-crafted file which could be used to launch a privileged shell instance. This issue affects Avast Antivirus prior to 24.2.

Time-of-check to time-of-use (TOCTOU) bug leads to full local privilege escalation.

A time-of-check to time-of-use (TOCTOU) bug in handling of IOCTL (input/output control) requests. This TOCTOU bug leads to an out-of-bounds write vulnerability which can be further exploited, allowing an attacker to gain full local privilege escalation on the system.This issue affects Avast/Avg Antivirus: 23.8.

Multiple DLL hijacking vulnerabilities via the components instup.exe and wsc_proxy.exe in Avast Premium Security before v21.11.2500 allows attackers to execute arbitrary code or cause a Denial of Service (DoS) via a crafted DLL file.

An arbitrary file write vulnerability in Avast Premium Security before v21.11.2500 (build 21.11.6809.528) allows attackers to cause a Denial of Service (DoS) via a crafted DLL file.

Privilege escalation vulnerability in Avast Antivirus prior to 20.4 allows a local user to gain elevated privileges by "hollowing" trusted process which could lead to the bypassing of Avast self-defense.

Multiple privilege escalation vulnerabilities in Avast Antivirus prior to 20.4 allow a local user to gain elevated privileges by calling unnecessarily powerful internal methods of the main antivirus service which could lead to the (1) arbitrary file delete, (2) write and (3) reset security.

Privilege escalation vulnerability in the Self-Defense driver of Avast Antivirus prior to 20.8 allows a local user with SYSTEM privileges to gain elevated privileges by "hollowing" process wsc_proxy.exe which could lead to acquire antimalware (AM-PPL) protection.

Privilege escalation vulnerability in the Sandbox component of Avast Antivirus prior to 20.4 allows a local sandboxed code to gain elevated privileges by using system IPC interfaces which could lead to exit the sandbox and acquire SYSTEM privileges.

Sandbox component in Avast Antivirus prior to 20.4 has an insecure permission which could be abused by local user to control the outcome of scans, and therefore evade detection or delete arbitrary system files.

This vulnerability allows local attackers to delete arbitrary directories on affected installations of Avast Premium Security 20.8.2429 (Build 20.8.5653.561). An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the AvastSvc.exe module. By creating a directory junction, an attacker can abuse the service to delete a directory. An attacker can leverage this vulnerability to create a denial-of-service condition on the system. Was ZDI-CAN-12082.

The Avast AV parsing engine allows virus-detection bypass via a crafted ZIP archive. This affects versions before 12 definitions 200114-0 of Antivirus Pro, Antivirus Pro Plus, and Antivirus for Linux.

Avast AntiTrack before 1.5.1.172 and AVG Antitrack before 2.0.0.178 proxies traffic to HTTPS sites but does not validate certificates, and thus a man-in-the-middle can host a malicious website using a self-signed certificate. No special action necessary by the victim using AntiTrack with "Allow filtering of HTTPS traffic for tracking detection" enabled. (This is the default configuration.)