CVE-2025-24014: Vim Use-After-Free Vulnerability

CVE-2025-24014 Overview

A segmentation fault vulnerability has been identified in Vim, the popular open source command line text editor. The vulnerability exists in Vim versions before 9.1.1043 and can be triggered when Vim is operating in silent Ex mode (-s -e). In this mode, Vim typically operates silently in batch mode without displaying a screen. However, by feeding specific binary characters to Vim, an attacker can trigger the scrolling function designed for the GUI version, which attempts to access the ScreenLines pointer—a variable that hasn't been allocated since no screen exists in silent mode. This results in an out-of-bounds memory access leading to a segmentation fault.

Critical Impact

This vulnerability (CWE-787: Out-of-Bounds Write) can cause Vim to crash when processing maliciously crafted input in silent Ex mode, potentially leading to denial of service or unexpected application behavior in automated scripts and batch processing workflows.

Affected Products

• Vim versions prior to 9.1.1043
• NetApp HCI Compute Node Firmware
• NetApp HCI Compute Node

Discovery Timeline

• 2025-01-20 - CVE-2025-24014 published to NVD
• 2025-08-14 - Last updated in NVD database

Technical Details for CVE-2025-24014

Vulnerability Analysis

The vulnerability stems from improper memory access in Vim's scrolling and screen update functions when the editor is running in silent Ex mode. When Vim operates with the -s -e flags, it enters a batch processing mode where no screen buffer is allocated since visual output is unnecessary. However, the code path that handles GUI scrolling operations does not properly validate whether the screen buffer exists before attempting to access it.

The core issue is that the updateWindow() function can be invoked through scrolling operations triggered by binary character input, which subsequently attempts to redraw the screen. This redraw operation accesses the ScreenLines pointer, which remains NULL in silent Ex mode because no display initialization occurs. Dereferencing this null pointer causes a segmentation fault, terminating the Vim process unexpectedly.

Root Cause

The root cause is a missing null pointer check for the ScreenLines variable in the GUI scrolling code path within src/gui.c. The updateWindow() function was being called without first verifying that a valid display context existed, leading to null pointer dereference when Vim operates without screen initialization.

Attack Vector

This is a local attack vector that requires an attacker to either have direct access to execute Vim with specific flags or the ability to influence input fed to Vim processes running in silent Ex mode. The attack requires:

1. Vim running in silent Ex mode (-s -e flags)
2. Ability to feed binary characters to the Vim process that trigger scrolling functions
3. The scrolling function triggers a redraw attempt on unallocated screen memory

The following patch from the official Vim repository addresses the vulnerability by adding a null check for ScreenLines:

    /*
     * Don't call updateWindow() when nothing has changed (it will overwrite
     * the status line!).
     *
     * Check for ScreenLines, because in ex-mode, we don't have a valid display.
     */
    if (ScreenLines != NULL && (old_topline != wp->w_topline
	    || wp->w_redr_type != 0
#ifdef FEAT_DIFF
	    || old_topfill != wp->w_topfill
#endif
	    ))
    {
	int type = UPD_VALID;

Source: GitHub Commit 9d1bed5

Detection Methods for CVE-2025-24014

Indicators of Compromise

• Unexpected Vim process crashes or segmentation faults in system logs
• Core dumps generated by Vim processes running with -s -e flags
• Abnormal input patterns containing binary characters being fed to batch Vim operations
• Increased frequency of Vim process terminations in automated scripting environments

Detection Strategies

• Monitor system logs for segmentation fault signals (SIGSEGV) from Vim processes
• Implement process monitoring to detect abnormal Vim terminations during batch operations
• Review audit logs for Vim executions with silent Ex mode flags (-s -e)
• Deploy endpoint detection to identify suspicious binary input being piped to Vim processes

Monitoring Recommendations

• Enable core dump collection for Vim processes to facilitate forensic analysis
• Set up alerting for repeated Vim crashes in production batch processing systems
• Monitor for unusual process spawning patterns involving Vim with Ex mode flags
• Implement file integrity monitoring on Vim binaries to ensure patched versions are deployed

How to Mitigate CVE-2025-24014

Immediate Actions Required

• Upgrade Vim to version 9.1.1043 or later immediately
• Review and audit all automated scripts that invoke Vim in silent Ex mode
• Validate input sources for any batch Vim operations to prevent untrusted binary input
• Consider restricting Vim execution in sensitive environments until patches are applied

Patch Information

The vulnerability is fixed in Vim version 9.1.1043. The official patch adds a null pointer check for ScreenLines before attempting screen update operations. The fix ensures that updateWindow() is only called when a valid display context exists.

Patch resources:

• GitHub Security Advisory GHSA-j3g9-wg22-v955
• GitHub Commit 9d1bed5
• NetApp Security Advisory

Workarounds

• Avoid running Vim in silent Ex mode (-s -e) with untrusted input until patched
• Implement input validation/sanitization for any data fed to Vim batch processes
• Consider using alternative text processing tools for automated workflows until upgrade is complete
• Deploy application sandboxing to limit the impact of potential crashes

# Check current Vim version
vim --version | head -1

# Update Vim on Debian/Ubuntu
sudo apt update && sudo apt install vim

# Update Vim on RHEL/CentOS
sudo yum update vim

# Verify updated version is 9.1.1043 or later
vim --version | grep -E "Included patches.*1043"