CVE-2022-0417: Vim Heap-Based Buffer Overflow Vulnerability

CVE-2022-0417 Overview

A heap-based buffer overflow vulnerability exists in the Vim text editor in versions prior to 8.2. This vulnerability is classified as CWE-122 (Heap-based Buffer Overflow) and CWE-787 (Out-of-Bounds Write), indicating memory corruption issues that can occur when processing certain input data. The vulnerability requires local access and user interaction to exploit, where an attacker could craft malicious input that triggers illegal memory access through the :retab command.

Critical Impact

Successful exploitation could lead to confidentiality, integrity, and availability compromise on affected systems, potentially allowing attackers to execute arbitrary code or cause denial of service conditions.

Affected Products

• Vim versions prior to 8.2
• Fedora 34 and 35
• Debian Linux 9.0 and 10.0

Discovery Timeline

• 2022-02-01 - CVE-2022-0417 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2022-0417

Vulnerability Analysis

This heap-based buffer overflow vulnerability stems from improper bounds checking when handling tab stop values in Vim. The vulnerability manifests in the :retab command functionality, where providing a value of 0 or excessively large values could cause illegal memory access. The attack requires local access with user interaction, meaning an attacker would need to convince a user to open a maliciously crafted file or execute a specifically crafted command. Upon successful exploitation, attackers could potentially achieve code execution within the context of the Vim process, compromise data confidentiality and integrity, or cause the application to crash.

Root Cause

The root cause lies in insufficient validation of tab stop values in the src/indent.c and src/option.c source files. The original code allowed tab stop values that could exceed safe bounds, with the validation only checking against an arbitrary limit of 9999 rather than a properly defined maximum (TABSTOP_MAX). Additionally, the tabstop option (b_p_ts) lacked upper bound validation, allowing excessively large values to be set.

Attack Vector

The attack vector is local, requiring user interaction. An attacker would need to craft a malicious Vim script or file that sets extreme tab stop values, then convince a target user to open the file or execute the commands. When the victim processes the malicious input using the :retab command with a value of 0 or an extremely large number, the heap-based buffer overflow is triggered, potentially leading to memory corruption and code execution.

The security patch addresses the issue by introducing proper bounds checking:

 	int n = atoi((char *)cp);
 
 	// Catch negative values, overflow and ridiculous big values.
-	if (n < 0 || n > 9999)
+	if (n < 0 || n > TABSTOP_MAX)
 	{
 	    semsg(_(e_invalid_argument_str), cp);
 	    vim_free(*array);

Source: GitHub Commit

Additional validation was added for the tabstop option:

 	errmsg = e_argument_must_be_positive;
 	curbuf->b_p_ts = 8;
     }
+    else if (curbuf->b_p_ts > TABSTOP_MAX)
+    {
+	errmsg = e_invalid_argument;
+	curbuf->b_p_ts = 8;
+    }
     if (p_tm < 0)
     {
 	errmsg = e_argument_must_be_positive;

Source: GitHub Commit

Detection Methods for CVE-2022-0417

Indicators of Compromise

• Vim process crashes or unexpected termination when opening files
• Memory corruption errors in system logs related to Vim execution
• Unusual Vim commands in shell history, particularly :retab with extreme values
• Presence of suspicious .vim files or vimrc configurations with abnormal tabstop settings

Detection Strategies

• Monitor for Vim process crashes and analyze core dumps for heap corruption patterns
• Implement file integrity monitoring on Vim configuration files to detect malicious modifications
• Use endpoint detection solutions to identify exploitation attempts targeting text editors
• Deploy memory protection mechanisms such as ASLR and DEP to mitigate exploitation success

Monitoring Recommendations

• Enable audit logging for Vim process executions and monitor for abnormal command patterns
• Configure system monitoring to alert on repeated Vim crashes that may indicate exploitation attempts
• Review downloaded files and email attachments for suspicious Vim script content before execution

How to Mitigate CVE-2022-0417

Immediate Actions Required

• Update Vim to version 8.2 or later immediately
• Review and audit any untrusted Vim scripts or configuration files before execution
• Consider restricting Vim's ability to execute external commands in sensitive environments
• Apply operating system vendor patches for Fedora and Debian systems

Patch Information

The vulnerability has been addressed in Vim version 8.2 through commit 652dee448618589de5528a9e9a36995803f5557a. The fix introduces a proper constant TABSTOP_MAX for bounds checking and adds validation in both src/indent.c and src/option.c to prevent illegal memory access. Users should update to the patched version through their distribution's package manager or by compiling from the official Vim GitHub repository. Vendor advisories are available from Debian LTS, Fedora, and Gentoo.

Workarounds

• Avoid opening untrusted files with Vim until patches are applied
• Use alternative text editors for handling files from untrusted sources
• Run Vim in restricted mode (vim -Z) when editing potentially malicious files
• Implement sandboxing or containerization when working with untrusted content

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

# Update Vim on Fedora systems
sudo dnf update vim

# Verify installed Vim version
vim --version | head -1