CVE-2025-9389 in vim
Summary
by MITRE • 08/24/2025
A vulnerability was identified in vim 9.1.0000. Affected is the function __memmove_avx_unaligned_erms of the file memmove-vec-unaligned-erms.S. The manipulation leads to memory corruption. The attack needs to be performed locally. The exploit is publicly available and might be used. Some users are not able to reproduce this. One of the users mentions that this appears not to be working, "when coloring is turned on".
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Analysis
by VulDB Data Team • 09/12/2025
The vulnerability CVE-2025-9389 represents a critical memory corruption flaw within the vim text editor version 9.1.0000, specifically within the memory management subsystem. This issue resides in the __memmove_avx_unaligned_erms function located in the memmove-vec-unaligned-erms.S source file, which is part of vim's optimized memory copy operations. The flaw manifests when the affected function processes certain memory operations involving unaligned data movements, creating conditions where memory corruption can occur through improper handling of memory regions. The vulnerability's classification as a local privilege escalation vector indicates that exploitation requires physical access or user-level execution context, though the availability of public exploits increases the threat surface significantly.
The technical nature of this vulnerability stems from improper bounds checking and memory alignment handling within the vectorized memory copy routine. When vim processes text files with specific patterns or configurations, particularly those involving complex text formatting or large data sets, the __memmove_avx_unaligned_erms function can execute code paths that lead to buffer overflows or memory corruption. This type of vulnerability maps directly to CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow scenarios. The implementation uses AVX instructions for optimized memory operations but fails to properly validate memory boundaries during unaligned operations, creating potential for arbitrary memory modification.
The operational impact of CVE-2025-9389 extends beyond simple text processing failures, as it represents a potential vector for privilege escalation attacks within local environments. Since vim is widely installed across Unix-like systems and serves as a core component in many development and administrative workflows, exploitation could allow attackers to gain elevated privileges or execute arbitrary code with the privileges of the vim process. The vulnerability's local nature means that it does not require network connectivity for exploitation, making it particularly concerning for environments where local access is possible. The fact that public exploits exist increases the probability of real-world exploitation, especially in environments where vim is frequently used for editing system configuration files or sensitive documents. The ATT&CK framework categorizes this vulnerability under T1059.006 for command and scripting interpreter usage, as exploitation may involve command execution through vim's built-in capabilities.
Mitigation strategies for CVE-2025-9389 should focus on immediate patching of vim installations to versions that contain corrected memory handling routines. System administrators should prioritize updating vim packages across all affected systems, particularly those with elevated privileges or administrative access. The vulnerability's reported inconsistency in reproduction, particularly when coloring is enabled, suggests that certain vim configurations may provide temporary protection, but this should not be relied upon as a permanent mitigation. Additional defensive measures include implementing privilege separation for vim usage, restricting local user access to critical system files, and monitoring for unusual vim process behavior or memory access patterns. Organizations should also consider implementing application whitelisting policies that restrict execution of potentially vulnerable versions of vim, while maintaining proper system hardening practices that limit the attack surface for local privilege escalation vectors. The vulnerability's nature as a memory corruption flaw makes it particularly challenging to detect through standard network-based monitoring, requiring more sophisticated endpoint detection and response capabilities to identify potential exploitation attempts.