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 a specially designed file. Successful exploitation could lead to remote code execution (RCE) and complete system compromise.
Step 1: Payload Delivery: The attacker crafts a malicious file, potentially in a supported format (e.g., a specific file type Vim can open).
Step 2: File Opening: The victim opens the malicious file using Vim.
Step 3: Triggering the Vulnerability: Vim processes the file, and a specific sequence of operations or file content triggers the Use-After-Free condition. This could involve specific editing commands, file format parsing, or other internal operations.
Step 4: Memory Corruption: The Use-After-Free occurs, leading to memory corruption. A pointer to a previously freed memory location is accessed.
Step 5: Controlled Overwrite: The attacker's crafted file is designed to overwrite memory regions with attacker-controlled data, such as shellcode or function pointers.
Step 6: Code Execution: When the corrupted memory is later used by Vim, the attacker's code is executed, leading to arbitrary code execution and system compromise.
The vulnerability, CVE-2021-4192, is a Use-After-Free (UAF) in Vim. This occurs when a pointer to a memory location is freed, but the program continues to use that pointer. Specifically, the flaw resides in how Vim handles certain file formats or specific editing operations. The root cause is likely related to incorrect handling of dynamically allocated memory during the processing of a crafted input file. When a specific sequence of operations is performed, a memory region is freed, and subsequent operations attempt to access that freed memory. This leads to a crash or, more critically, allows an attacker to control the contents of the freed memory, potentially overwriting critical data structures and achieving arbitrary code execution. The vulnerability is triggered by opening a malicious file or editing a file in a specific way, leading to a heap corruption scenario. The attacker can then control the execution flow by crafting the input file to overwrite function pointers or other sensitive data in memory.