CVE-2022-0554: Vim Buffer Overflow Vulnerability

CVE-2022-0554 Overview

CVE-2022-0554 is an Out-of-range Pointer Offset vulnerability affecting Vim text editor versions prior to 8.2. This memory corruption flaw stems from improper handling of buffer pointers in the jump list functionality, which can lead to memory access outside of intended boundaries.

Critical Impact

Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code with the privileges of the user running Vim, potentially leading to complete system compromise through local attack vectors requiring user interaction.

Affected Products

• Vim versions prior to 8.2
• Fedora 34
• Debian Linux 9.0 and 10.0
• Apple macOS (various versions)

Discovery Timeline

• 2022-02-10 - CVE-2022-0554 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-0554

Vulnerability Analysis

The vulnerability exists within Vim's buffer management code, specifically in src/buffer.c. The flaw involves improper handling of quickfix buffers during jump list traversal operations. When processing the jump list, the code could access buffer pointers that reference memory locations outside the valid range, constituting a CWE-823 (Use of Out-of-range Pointer Offset) and CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) weakness.

The issue arises when Vim iterates through the window's jump list to find valid buffers. The original implementation only checked if a buffer was the current buffer or unlisted, but failed to account for quickfix buffers that could be deleted during the operation. This oversight created a condition where the code could operate on a buffer that no longer exists in valid memory space.

Root Cause

The root cause is insufficient validation when accessing buffer pointers from the jump list. The buflist_findnr() function returns a buffer pointer based on the jump list entry, but the subsequent validation logic did not properly account for quickfix buffers. These special buffers can be deleted asynchronously, leading to dangling pointer access or out-of-range memory operations.

Attack Vector

This vulnerability requires local access with user interaction. An attacker would need to craft a malicious file or Vim configuration that triggers specific jump list operations involving quickfix buffers. When a user opens or processes the malicious content in Vim, the out-of-range pointer access could be exploited to achieve arbitrary code execution.

The following patch was applied to fix the vulnerability in src/buffer.c:

 		buf = buflist_findnr(curwin->w_jumplist[jumpidx].fmark.fnum);
 		if (buf != NULL)
 		{
-		    if (buf == curbuf || !buf->b_p_bl)
-			buf = NULL;	// skip current and unlisted bufs
+		    // Skip current and unlisted bufs.  Also skip a quickfix
+		    // buffer, it might be deleted soon.
+		    if (buf == curbuf || !buf->b_p_bl
+#if defined(FEAT_QUICKFIX)
+			    || bt_quickfix(buf)
+#endif
+			    )
+			buf = NULL;
 		    else if (buf->b_ml.ml_mfp == NULL)
 		    {
 			// skip unloaded buf, but may keep it for later

Source: GitHub Vim Commit

Detection Methods for CVE-2022-0554

Indicators of Compromise

• Unexpected Vim crashes or segmentation faults during normal editing operations
• Vim process consuming abnormal amounts of memory or exhibiting erratic behavior
• Suspicious Vim configuration files or modelines in documents
• Evidence of quickfix buffer manipulation in Vim session files

Detection Strategies

• Monitor for Vim processes exhibiting memory access violations or crashes
• Implement endpoint detection rules for Vim instances processing unusual file types or configurations
• Audit systems for Vim versions below 8.2.4327 using package management queries
• Deploy SentinelOne agents to detect exploitation attempts through behavioral analysis

Monitoring Recommendations

• Enable crash reporting and core dump analysis for Vim processes
• Monitor for attempts to execute Vim with suspicious command-line arguments or scripts
• Implement file integrity monitoring for Vim configuration directories (~/.vim, /etc/vim)
• Track Vim version inventories across the environment to identify unpatched systems

How to Mitigate CVE-2022-0554

Immediate Actions Required

• Update Vim to version 8.2.4327 or later on all affected systems
• Disable automatic execution of modelines by adding set nomodeline to Vim configuration
• Restrict Vim usage to trusted files until patches are applied
• Consider using Neovim as an alternative if immediate patching is not possible

Patch Information

The vulnerability was addressed in Vim patch 8.2.4327 through commit e3537aec2f8d6470010547af28dcbd83d41461b8. The fix adds a check to skip quickfix buffers during jump list traversal, preventing access to buffers that might be deleted. Multiple distributions have released security updates:

• Debian LTS Security Announcement
• Fedora Package Announcement
• Gentoo GLSA Report
• Apple Support Security Article

Workarounds

• Add set nomodeline to your .vimrc to prevent automatic modeline execution
• Avoid opening untrusted files in Vim until patched
• Use vim -u NONE to start Vim without loading plugins or configurations when handling suspicious files
• Restrict file system permissions on Vim configuration directories

# Configuration example to disable modelines
echo "set nomodeline" >> ~/.vimrc

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

# Update Vim on Fedora systems
sudo dnf update vim

# Update Vim on macOS via Homebrew
brew upgrade vim