Source: cert@airbus.com
Avira Free Antivirus 15.0.1907.1514 is prone to a local privilege escalation through the execution of kernel code from a restricted user.
Avira Free Antivirus 15.0.1907.1514 is vulnerable to a local privilege escalation, allowing a restricted user to execute arbitrary code with kernel-level privileges. This vulnerability could lead to complete system compromise, enabling attackers to install malware, steal sensitive data, and gain persistent access to the compromised machine.
Step 1: Triggering the Vulnerability: The attacker, operating with restricted user privileges, identifies a specific operation or function within Avira's kernel-mode driver that is vulnerable. This could involve interacting with a specific device driver or calling a particular API function.
Step 2: Crafting a Malicious Input: The attacker crafts a malicious input, such as a specially formatted file, a crafted network packet, or a specific sequence of API calls, designed to exploit the vulnerability. This input is designed to trigger the vulnerability and manipulate the driver's internal state.
Step 3: Input Processing and Exploitation: The attacker's crafted input is processed by the vulnerable kernel code. Due to the lack of proper validation, the malicious input leads to a memory corruption condition, such as a buffer overflow or use-after-free condition.
Step 4: Code Execution: The memory corruption allows the attacker to overwrite critical data structures or hijack the control flow of the kernel code. This enables the attacker to execute arbitrary code within the kernel context.
Step 5: Privilege Escalation: The attacker's code, executing in the kernel, gains elevated privileges, effectively bypassing the security restrictions of the restricted user account. This allows the attacker to perform actions that a normal user would not be able to do, such as installing malware, modifying system files, or accessing sensitive data.
The vulnerability stems from a flaw in how Avira's antivirus software handles certain operations, likely related to its kernel-mode drivers. The software likely fails to properly validate user-supplied input or parameters before passing them to a privileged function within the kernel. This could manifest as a type confusion, integer overflow, or a similar memory corruption vulnerability. The attacker can then craft a malicious input that, when processed by the vulnerable kernel code, leads to the execution of arbitrary code within the kernel context. This could involve overwriting critical data structures, hijacking control flow, or directly calling kernel functions with malicious arguments. The root cause is a lack of proper input validation and sanitization, combined with insufficient access control mechanisms within the kernel-mode driver.
While no specific APT groups are definitively linked to this CVE, any threat actor with the resources and motivation to develop or acquire an exploit could leverage this vulnerability. This includes financially motivated cybercriminals, state-sponsored actors, and other malicious groups. CISA KEV status: Not Listed.
Monitor system logs for unusual activity related to Avira processes, especially those interacting with kernel-mode drivers.
Analyze memory dumps for signs of memory corruption or malicious code execution within the Avira kernel drivers.
Monitor network traffic for any unusual communication patterns originating from the affected system, particularly if associated with Avira processes.
Implement host-based intrusion detection systems (HIDS) to detect suspicious file modifications or process behavior.
Use endpoint detection and response (EDR) solutions to identify and respond to malicious activity.
Monitor for the creation of suspicious files or registry entries associated with the exploit.
Analyze process creation events for unusual parent-child relationships involving Avira processes.
Update Avira Free Antivirus to the latest version. This is the primary and most effective remediation step.
Implement a robust patch management strategy to ensure that all software is kept up-to-date.
Restrict user privileges to the minimum necessary for their job functions.
Implement application whitelisting to prevent the execution of unauthorized programs.
Regularly audit system logs and security configurations.
Implement a defense-in-depth strategy, including firewalls, intrusion detection systems, and endpoint security solutions.
Consider using a host-based intrusion prevention system (HIPS) to monitor and block suspicious activity.
Enable kernel-mode code signing enforcement to prevent the execution of unsigned or malicious kernel drivers.