CVE-2022-1619: Vim Buffer Overflow Vulnerability

CVE-2022-1619 Overview

CVE-2022-1619 is a heap-based buffer overflow vulnerability affecting the cmdline_erase_chars function in the Vim text editor. This vulnerability exists in Vim versions prior to 8.2.4899 and occurs when processing command line character erasure operations with latin1 encoding. The flaw can lead to software crashes, memory corruption, and potentially enable remote code execution when a user opens a specially crafted file.

Critical Impact

A heap-based buffer overflow in Vim's command line processing that can crash the application, corrupt memory, and potentially allow code execution when processing malicious input.

Affected Products

• Vim versions prior to 8.2.4899
• Fedora 34, 35, and 36
• Debian Linux 9.0 and 10.0
• NetApp HCI Management Node
• NetApp SolidFire
• Apple macOS (various versions)

Discovery Timeline

• May 8, 2022 - CVE-2022-1619 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-1619

Vulnerability Analysis

The vulnerability resides in the cmdline_erase_chars function within Vim's src/ex_getln.c source file. When using latin1 encoding and pressing CTRL-W to delete a word in command line mode, the function fails to properly validate buffer boundaries before performing pointer arithmetic operations. This allows the pointer to traverse before the beginning of the command line buffer (ccline.cmdbuff), resulting in a heap-based buffer overflow condition.

The flaw is classified under CWE-122 (Heap-based Buffer Overflow) and CWE-787 (Out-of-bounds Write), indicating that the vulnerability allows writing data outside the allocated heap buffer boundaries. The local attack vector requires user interaction—specifically, a victim must open a maliciously crafted file or be tricked into executing specific command line operations.

Root Cause

The root cause is a missing boundary check in the word deletion logic of the command line interface. When erasing characters from the command line, the code decrements a pointer p while checking for word characters and whitespace, but it does not verify that p remains within the valid buffer range before calling vim_iswordc(p[-1]). This allows the pointer to move before the start of the allocated buffer, leading to out-of-bounds memory access.

Attack Vector

The vulnerability requires local access and user interaction to exploit. An attacker could craft a malicious file that, when opened in Vim, triggers the vulnerable code path through specific command line operations. When a user presses CTRL-W to delete a word while in command line mode with latin1 encoding enabled, the improper boundary handling can corrupt heap memory. This could potentially be chained with other techniques to achieve code execution with the privileges of the Vim process.

// Vulnerable code path in src/ex_getln.c (before patch)
{
    while (p > ccline.cmdbuff && vim_isspace(p[-1]))
        --p;
    i = vim_iswordc(p[-1]);  // Missing boundary check here
    while (p > ccline.cmdbuff && !vim_isspace(p[-1])
            && vim_iswordc(p[-1]) == i)
        --p;
}

Source: GitHub Vim Commit

Detection Methods for CVE-2022-1619

Indicators of Compromise

• Unexpected Vim process crashes or segmentation faults when performing command line operations
• Core dumps indicating heap corruption in Vim processes
• Abnormal memory access patterns in process monitoring related to Vim execution
• System logs showing Vim termination due to memory violations

Detection Strategies

• Monitor for Vim crashes that occur during command line editing operations, particularly when using CTRL-W
• Implement file integrity monitoring to detect unauthorized modifications to Vim binaries
• Use memory protection tools like AddressSanitizer (ASAN) during development to detect buffer overflows
• Deploy endpoint detection rules that alert on suspicious Vim process behavior or unexpected termination

Monitoring Recommendations

• Enable crash reporting and analysis for Vim processes across endpoints
• Monitor package management systems to verify Vim versions are updated to 8.2.4899 or later
• Implement centralized logging for application crashes to identify potential exploitation attempts
• Review system audit logs for unusual file access patterns preceding Vim crashes

How to Mitigate CVE-2022-1619

Immediate Actions Required

• Update Vim to version 8.2.4899 or later immediately on all affected systems
• Apply vendor-specific patches from Fedora, Debian, Apple, or NetApp as applicable to your environment
• Restrict Vim usage on critical systems until patches can be applied
• Educate users about the risks of opening untrusted files in Vim

Patch Information

The vulnerability has been addressed in Vim version 8.2.4899. The fix adds proper boundary validation before accessing buffer memory in the cmdline_erase_chars function. The patch ensures that the pointer remains within valid buffer boundaries before attempting to read character values.

Patched code from commit ef02f16609ff0a26ffc6e20263523424980898fe:

// Fixed code with proper boundary check
{
    while (p > ccline.cmdbuff && vim_isspace(p[-1]))
        --p;
    if (p > ccline.cmdbuff)  // Added boundary check
    {
        i = vim_iswordc(p[-1]);
        while (p > ccline.cmdbuff && !vim_isspace(p[-1])
                && vim_iswordc(p[-1]) == i)
            --p;
    }
}

Source: GitHub Vim Commit

Vendor-specific patches are available:

• Apple Support Article HT213488
• Debian LTS Announcement May 2022
• NetApp Security Advisory NTAP-20220930-0007
• Gentoo GLSA 2022-08-32

Workarounds

• Avoid using CTRL-W for word deletion in command line mode until the system is patched
• Consider using alternative text editors for handling untrusted files
• Implement application whitelisting to prevent execution of potentially compromised Vim binaries
• Use containerized or sandboxed environments when editing files from untrusted sources

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

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

# Update Vim on Fedora
sudo dnf update vim

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