CVE-2022-2343: Vim Buffer Overflow Vulnerability

CVE-2022-2343 Overview

CVE-2022-2343 is a heap-based buffer overflow vulnerability affecting Vim, the popular text editor, in versions prior to 9.0.0044. The vulnerability exists in the completion functionality where insufficient bounds checking allows an attacker to read past the end of allocated memory when processing specially crafted input with long lines.

Critical Impact

This heap-based buffer overflow vulnerability can potentially lead to arbitrary code execution, information disclosure, or denial of service when a user opens a malicious file or triggers completion on specially crafted content.

Affected Products

• Vim versions prior to 9.0.0044
• Fedora 35

Discovery Timeline

• 2022-07-08 - CVE-2022-2343 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-2343

Vulnerability Analysis

The vulnerability is classified as CWE-122 (Heap-based Buffer Overflow) and resides in Vim's insert completion functionality within the src/insexpand.c source file. The flaw occurs when the ins_compl_infercase_gettext() function processes completion text for long lines. The original implementation incorrectly calculated buffer lengths, leading to reading past the end of allocated heap memory during case inference operations for completions.

The vulnerability requires local access and user interaction to exploit, as a victim must open a maliciously crafted file or trigger completion on crafted content. Successful exploitation could lead to arbitrary code execution with the privileges of the user running Vim, potentially allowing an attacker to gain control of the affected system.

Root Cause

The root cause lies in the ins_compl_infercase_gettext() function in src/insexpand.c. The function was allocating a wide character array based on actual_len for completion processing, but the bounds checking for operations on this buffer was insufficient. When processing completions with long lines, the function could read past the end of the allocated buffer, causing a heap buffer over-read condition.

Attack Vector

The attack vector is local, requiring user interaction. An attacker could craft a malicious file that, when opened in Vim and when the user triggers autocompletion, exploits the buffer overflow condition. The attack could be delivered through:

1. Malicious source code files shared in repositories
2. Specially crafted configuration files
3. Text files designed to trigger the vulnerable code path when completion is invoked

// Security patch in src/insexpand.c - patch 9.0.0045
// Source: https://github.com/vim/vim/commit/caea66442d86e7bbba3bf3dc202c3c0d549b9853

 
 /*
  * Get the completed text by inferring the case of the originally typed text.
+ * If the result is in allocated memory "tofree" is set to it.
  */
     static char_u *
 ins_compl_infercase_gettext(
 	char_u	*str,
-	int	actual_len,
-	int	actual_compl_length,
-	int	min_len)
+	int	char_len,
+	int	compl_char_len,
+	int	min_len,
+	char_u  **tofree)
 {
     int		*wca;			// Wide character array.
     char_u	*p;
     int		i, c;
     int		has_lower = FALSE;
     int		was_letter = FALSE;
+    garray_T	gap;
 
     IObuff[0] = NUL;
 
     // Allocate wide character array for the completion and fill it.
-    wca = ALLOC_MULT(int, actual_len);
+    wca = ALLOC_MULT(int, char_len);
     if (wca == NULL)
 	return IObuff;

Detection Methods for CVE-2022-2343

Indicators of Compromise

• Unexpected Vim process crashes or segmentation faults during autocompletion operations
• Abnormal memory access patterns in Vim processes when processing text files
• Core dumps from Vim processes showing heap corruption artifacts

Detection Strategies

• Monitor Vim processes for abnormal behavior such as unexpected crashes or high memory usage during file editing operations
• Implement file integrity monitoring on systems where Vim is commonly used to detect potential malicious file introductions
• Use endpoint detection solutions to identify exploitation attempts targeting memory corruption vulnerabilities

Monitoring Recommendations

• Deploy SentinelOne agents to monitor for suspicious process behavior and memory access anomalies in text editor applications
• Enable crash dump collection and analysis to identify potential exploitation attempts
• Implement version tracking for Vim installations across the enterprise to identify vulnerable instances

How to Mitigate CVE-2022-2343

Immediate Actions Required

• Update Vim to version 9.0.0045 or later immediately on all affected systems
• For systems that cannot be immediately patched, consider restricting Vim usage to trusted files only
• Review and audit any Vim installations across the organization for version compliance

Patch Information

The vulnerability was addressed in Vim patch 9.0.0045. The fix modifies the ins_compl_infercase_gettext() function to properly handle character length calculations and adds a tofree parameter for safer memory management. The patch is available through the official Vim GitHub repository commit.

Linux distributions have also released security updates:

• Fedora has released updates via their package announcement
• Gentoo has issued GLSA 202208-32 and GLSA 202305-16

Workarounds

• Avoid opening untrusted files in Vim until the patch can be applied
• Disable autocompletion features temporarily by adding set complete= to your .vimrc configuration
• Use alternative text editors for processing files from untrusted sources

# Configuration example - Disable completion in Vim
# Add to ~/.vimrc to disable insert-mode completion
set complete=
set completeopt=

# Alternatively, check your current Vim version
vim --version | head -1

# Update Vim on Fedora-based systems
sudo dnf update vim

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