CVE-2021-4069 in vim
Summary
by MITRE • 12/06/2021
vim is vulnerable to Use After Free
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Analysis
by VulDB Data Team • 12/09/2021
The vulnerability identified as CVE-2021-4069 represents a critical use after free condition within the vim text editor software. This flaw occurs when the application attempts to access memory that has already been freed or deallocated, creating a potential pathway for malicious code execution. The vulnerability specifically manifests during the processing of certain file formats or commands within vim's parsing mechanisms, where improper memory management leads to the reuse of freed memory regions. Such conditions are particularly dangerous because they can be exploited to execute arbitrary code with the privileges of the user running vim, potentially leading to complete system compromise.
The technical implementation of this use after free vulnerability stems from inadequate memory management practices within vim's internal codebase. When processing specific input sequences or file structures, the application allocates memory for data structures but fails to properly track their lifecycle. This results in scenarios where memory blocks are freed from the heap but references to these locations persist within the program's execution flow. The flaw typically occurs in contexts involving complex data manipulation or parsing of external input, where the software's memory allocation routines do not adequately prevent subsequent access to deallocated memory regions. This type of vulnerability is classified under CWE-416, which specifically addresses the use of freed memory conditions in software applications.
The operational impact of CVE-2021-4069 extends beyond simple privilege escalation, as it represents a fundamental security weakness that can be leveraged across multiple attack vectors. An attacker could exploit this vulnerability through various means including opening maliciously crafted files, processing specially constructed command sequences, or manipulating input data during editing operations. The vulnerability's severity is amplified by the widespread use of vim across Unix-like systems, making it a prime target for exploitation in environments where the editor is frequently used with untrusted content. The potential for remote code execution through this flaw means that systems running vulnerable versions of vim could be compromised without user interaction, particularly in scenarios where vim is used in automated processing or web-based environments.
Mitigation strategies for CVE-2021-4069 should focus on immediate patching of affected vim installations, as the vulnerability cannot be effectively addressed through configuration changes alone. System administrators should prioritize updating to patched versions of vim that have corrected the memory management issues, with particular attention to the specific commit or release that addresses the use after free condition. Additionally, implementing restrictive file access controls and sandboxing measures can help limit the potential impact of exploitation attempts. Organizations should also consider monitoring for suspicious vim usage patterns and implementing security awareness training to prevent users from inadvertently opening malicious files. The vulnerability's classification under ATT&CK technique T1059.006 for command and scripting interpreter usage highlights the importance of monitoring for unusual vim command execution patterns that might indicate exploitation attempts. Regular security audits of system components and maintaining up-to-date vulnerability assessments are essential practices for preventing exploitation of this and similar memory corruption vulnerabilities.