Source: security@huntr.dev
vim is vulnerable to Use After Free
Vim, a widely used text editor, suffers from a Use-After-Free (UAF) vulnerability, allowing attackers to potentially execute arbitrary code. This flaw arises from improper memory management, enabling malicious actors to gain control of a system by crafting specially designed files. Successful exploitation can lead to remote code execution (RCE) and complete system compromise.
Step 1: Payload Delivery: The attacker crafts a malicious file (e.g., a text file, a file with a specific format supported by Vim, or a file opened via a Vim plugin) designed to trigger the Use-After-Free vulnerability.
Step 2: File Opening/Processing: The victim opens the malicious file using Vim, or the file is automatically processed by Vim (e.g., via a plugin or a script).
Step 3: Vulnerability Trigger: Vim's code, while processing the file, encounters a specific sequence of operations that leads to the deallocation of a memory region.
Step 4: Memory Reuse: The freed memory region is later accessed by Vim, either directly or indirectly, due to a logic error or race condition. This access occurs after the memory has been freed.
Step 5: Code Execution: The attacker, through the crafted file, has controlled the contents of the memory region that is accessed after being freed. This allows the attacker to overwrite critical data structures or inject malicious code into the process's memory space.
Step 6: Arbitrary Code Execution: The overwritten data or injected code is executed, granting the attacker control over the victim's system, potentially leading to remote code execution (RCE).
The vulnerability, CVE-2021-4192, stems from a Use-After-Free condition within Vim's handling of certain file formats or specific editing operations. The root cause lies in the incorrect deallocation and subsequent reuse of memory associated with data structures used during file processing. Specifically, when Vim processes a crafted input file, it may free a memory region and then, due to a logic error or race condition, attempt to access that same freed memory. This can lead to the execution of attacker-controlled code if the freed memory is later reallocated and populated with malicious data. The specific function or code path responsible for the vulnerability is likely related to how Vim handles specific file types, such as those with complex formatting or embedded objects, or during certain editing operations. The attacker can control the contents of the freed memory, and therefore the subsequent execution flow.
Attackers are likely to leverage this vulnerability for initial access, privilege escalation, and lateral movement. APT groups and malware authors are likely to incorporate this vulnerability into their toolkits. CISA KEV status is likely, given the severity and ease of exploitation. Specific APT groups that might exploit this include, but are not limited to, those targeting Linux systems and developers.
Monitor file access patterns, especially for unusual file types or file extensions opened by Vim.
Analyze Vim process behavior for unexpected memory access patterns using tools like strace or memory analysis tools.
Examine system logs for suspicious activity related to Vim, such as crashes or errors during file processing.
Implement file integrity monitoring to detect modifications to Vim-related files or configurations.
Network monitoring for unusual outbound connections from systems running Vim, especially after opening suspicious files.
Analyze core dumps or crash reports generated by Vim for evidence of memory corruption or Use-After-Free errors.
Update Vim to the latest version, which includes patches for CVE-2021-4192.
Implement a robust patch management strategy to ensure timely application of security updates.
Restrict Vim's access to sensitive files and directories.
Disable or restrict the use of Vim plugins, especially those from untrusted sources.
Employ a file type whitelist to limit the types of files that can be opened with Vim.
Consider using a sandboxing solution to isolate Vim and limit its potential impact.
Regularly audit Vim configurations and security settings.