An issue was discovered in Avast Antivirus before 20. The aswTask RPC endpoint for the TaskEx library in the Avast Service (AvastSvc.exe) allows attackers to bypass intended access restrictions on tasks from an untrusted process, when Self Defense is enabled.

An issue was discovered in Avast Antivirus before 20. The aswTask RPC endpoint for the TaskEx library in the Avast Service (AvastSvc.exe) allows attackers to enumerate the network interfaces and access points from a Low Integrity process via RPC.

An issue was discovered in Avast Antivirus before 20. The aswTask RPC endpoint for the TaskEx library in the Avast Service (AvastSvc.exe) allows attackers to make arbitrary changes to the Components section of the Stats.ini file via RPC from a Low Integrity process.

An issue was discovered in Avast Antivirus before 20. The aswTask RPC endpoint for the TaskEx library in the Avast Service (AvastSvc.exe) allows attackers to trigger a reboot via RPC from a Low Integrity process.

An issue was discovered in Avast Antivirus before 20. The aswTask RPC endpoint for the TaskEx library in the Avast Service (AvastSvc.exe) allows attackers to trigger a shutdown via RPC from a Low Integrity process via TempShutDownMachine.

An issue was discovered in Avast Antivirus before 20. The aswTask RPC endpoint for the TaskEx library in the Avast Service (AvastSvc.exe) allows attackers to achieve Local Privilege Escalation (LPE) via RPC.

An issue was discovered in Avast Antivirus before 20. The aswTask RPC endpoint for the TaskEx library in the Avast Service (AvastSvc.exe) allows attackers to achieve Arbitrary File Deletion from Avast Program Path via RPC, when Self Defense is Enabled.

An issue was discovered in Avast Antivirus before 20. An Arbitrary Memory Address Overwrite vulnerability in the aswAvLog Log Library results in Denial of Service of the Avast Service (AvastSvc.exe).

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.)

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.

A Local Privilege Escalation issue was discovered in Avast Secure Browser 76.0.1659.101. The vulnerability is due to an insecure ACL set by the AvastBrowserUpdate.exe (which is running as NT AUTHORITY\SYSTEM) when AvastSecureBrowser.exe checks for new updates. When the update check is triggered, the elevated process cleans the ACL of the Update.ini file in %PROGRAMDATA%\Avast Software\Browser\Update\ and sets all privileges to group Everyone. Because any low-privileged user can create, delete, or modify the Update.ini file stored in this location, an attacker with low privileges can create a hard link named Update.ini in this folder, and make it point to a file writable by NT AUTHORITY\SYSTEM. Once AvastBrowserUpdate.exe is triggered by the update check functionality, the DACL is set to a misconfigured value on the crafted Update.ini and, consequently, to the target file that was previously not writable by the low-privileged attacker.

In Avast Premium Security 19.8.2393, attackers can send a specially crafted request to the local web server run by Avast Antivirus on port 27275 to support Bank Mode functionality. A flaw in the processing of a command allows execution of arbitrary OS commands with the privileges of the currently logged in user. This allows for example attackers who compromised a browser extension to escape from the browser sandbox.

XSS in the Video Downloader component before 1.5 of Avast Secure Browser 77.1.1831.91 and AVG Secure Browser 77.0.1790.77 allows websites to execute their code in the context of this component. While Video Downloader is technically a browser extension, it is granted a very wide set of privileges and can for example access cookies and browsing history, spy on the user while they are surfing the web, and alter their surfing experience in almost arbitrary ways.

A Cross Site Scripting (XSS) issue exists in Avast AntiVirus (Free, Internet Security, and Premiere Edition) 19.3.2369 build 19.3.4241.440 in the Network Notification Popup, allowing an attacker to execute JavaScript code via an SSID Name.

An issue was discovered in Avast antivirus before 19.8 and AVG antivirus before 19.8. A DLL Preloading vulnerability allows an attacker to implant %WINDIR%\system32\wbemcomn.dll, which is loaded into a protected-light process (PPL) and might bypass some of the self-defense mechanisms. This affects all components that use WMI, e.g., AVGSvc.exe 19.6.4546.0 and TuneupSmartScan.dll 19.1.884.0.

In Avast Antivirus before 19.4, a local administrator can trick the product into renaming arbitrary files by replacing the Logs\Update.log file with a symlink. The next time the product attempts to write to the log file, the target of the symlink is renamed. This defect can be exploited to rename a critical product file (e.g., AvastSvc.exe), causing the product to fail to start on the next system restart.

Avast Free Antivirus prior to 19.1.2360 stores user credentials in memory upon login, which allows local users to obtain sensitive information by dumping AvastUI.exe application memory and parsing the data.

The ThreadX-based firmware on Marvell Avastar Wi-Fi devices, models 88W8787, 88W8797, 88W8801, 88W8897, and 88W8997, allows remote attackers to execute arbitrary code or cause a denial of service (block pool overflow) via malformed Wi-Fi packets during identification of available Wi-Fi networks. Exploitation of the Wi-Fi device can lead to exploitation of the host application processor in some cases, but this depends on several factors including host OS hardening and the availability of DMA.

In Avast Antivirus before v17, an unprivileged user (and thus malware or a virus) can mark an arbitrary process as Trusted from the perspective of the Avast product. This bypasses the Self-Defense feature of the product, opening a door to subsequent attack on many of its components.

In Avast Antivirus before v17, using the LPC interface API exposed by the AvastSVC.exe Windows service, it is possible to launch predefined binaries, or replace or delete arbitrary files. This vulnerability is exploitable by any unprivileged user when Avast Self-Defense is disabled. It is also exploitable in conjunction with CVE-2017-8308 when Avast Self-Defense is enabled. The vulnerability allows for Denial of Service attacks and hiding traces of a possible attack.