CVE-2023-0054: Vim Buffer Overflow Vulnerability

CVE-2023-0054 Overview

CVE-2023-0054 is an out-of-bounds write vulnerability affecting Vim, the popular open-source text editor, in versions prior to 9.0.1145. This memory corruption flaw occurs during the handling of recursive substitute expressions, leading to invalid memory access that could potentially be exploited by an attacker to execute arbitrary code or cause denial of service conditions.

Critical Impact

Successful exploitation of this out-of-bounds write vulnerability could allow an attacker to corrupt memory, potentially leading to arbitrary code execution with the privileges of the user running Vim. The vulnerability requires user interaction, such as opening a maliciously crafted file.

Affected Products

• Vim versions prior to 9.0.1145
• Apple macOS systems with bundled Vim (addressed in HT213670)
• Debian and Gentoo Linux distributions with vulnerable Vim packages

Discovery Timeline

• 2023-01-04 - CVE-2023-0054 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2023-0054

Vulnerability Analysis

The vulnerability exists in Vim's substitute expression handling mechanism within the src/eval.c source file. When processing recursive substitute expressions, the application fails to properly validate the return value of the vim_regsub() function before proceeding with memory operations. This oversight allows the code to continue execution with invalid or unexpected data, resulting in writes to memory locations outside the intended buffer boundaries.

The flaw is classified as CWE-787 (Out-of-bounds Write), a dangerous memory corruption vulnerability class that can lead to code execution, data corruption, or application crashes. Exploitation requires local access and user interaction, such as convincing a user to open a specially crafted file in Vim.

Root Cause

The root cause of CVE-2023-0054 stems from insufficient validation of the sublen return value from the vim_regsub() function. Prior to the patch, the code would proceed to grow the buffer and perform memory operations even when vim_regsub() returned an error condition (indicated by a return value less than or equal to zero). This lack of error checking allowed invalid memory access scenarios during recursive substitute expression processing.

Attack Vector

An attacker could exploit this vulnerability by crafting a malicious Vim script or file containing specially designed recursive substitute expressions. When a victim opens or processes this file with an affected version of Vim, the invalid memory access occurs, potentially allowing the attacker to:

1. Corrupt adjacent memory structures
2. Achieve arbitrary code execution through controlled memory writes
3. Cause denial of service through application crashes

The attack vector is local, requiring the attacker to either have local access to the system or convince a user to open a malicious file.

// Security patch in src/eval.c - patch 9.0.1145
// Source: https://github.com/vim/vim/commit/3ac1d97a1d9353490493d30088256360435f7731

 	     * - The text after the match.
 	     */
 	    sublen = vim_regsub(®match, sub, expr, tail, 0, REGSUB_MAGIC);
+	    if (sublen <= 0)
+	    {
+		ga_clear(&ga);
+		break;
+	    }
 	    if (ga_grow(&ga, (int)((end - tail) + sublen -
 			    (regmatch.endp[0] - regmatch.startp[0]))) == FAIL)
 	    {

Detection Methods for CVE-2023-0054

Indicators of Compromise

• Unexpected Vim crashes or segmentation faults when opening files containing complex substitute expressions
• Core dump files generated by Vim processes indicating memory corruption
• Suspicious files with embedded recursive substitute patterns designed to trigger the vulnerability

Detection Strategies

• Monitor for Vim process crashes with memory violation signatures using system auditing tools
• Implement file integrity monitoring to detect suspicious Vim configuration files or scripts
• Use SentinelOne's behavioral AI to detect anomalous memory access patterns from Vim processes
• Deploy vulnerability scanning to identify systems running Vim versions prior to 9.0.1145

Monitoring Recommendations

• Enable crash reporting and core dump analysis on systems where Vim is frequently used
• Monitor system logs for repeated Vim segmentation faults that may indicate exploitation attempts
• Implement endpoint detection to track unusual child process spawning from Vim processes
• Use SentinelOne's Singularity platform to monitor for post-exploitation activity following Vim compromise

How to Mitigate CVE-2023-0054

Immediate Actions Required

• Upgrade Vim to version 9.0.1145 or later immediately on all affected systems
• Apply vendor-specific patches: Apple Security Update HT213670 for macOS systems
• Review and update Vim packages on Debian systems per the Debian LTS Announcement
• Gentoo users should apply updates per the GLSA-202305-16 Advisory

Patch Information

The vulnerability has been addressed in Vim version 9.0.1145 through commit 3ac1d97a1d9353490493d30088256360435f7731. The fix adds proper validation of the vim_regsub() return value, ensuring that error conditions are handled before proceeding with buffer operations. When the function returns a value less than or equal to zero, the code now clears the growing array and exits the operation safely.

Workarounds

• Avoid opening untrusted files with Vim until the patch can be applied
• Consider using alternative text editors for processing files from untrusted sources
• Restrict Vim execution permissions to trusted users only on shared systems
• Implement application whitelisting to control Vim execution in sensitive environments

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

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

# Update Vim on RHEL/CentOS systems
sudo yum update vim

# Update Vim on macOS via Homebrew
brew update && brew upgrade vim