CVE-2022-29458: GNU Ncurses Buffer Overflow Vulnerability

CVE-2022-29458 Overview

CVE-2022-29458 is an out-of-bounds read vulnerability affecting the ncurses library version 6.3 before patch 20220416. The vulnerability exists in the convert_strings function within tinfo/read_entry.c in the terminfo library. When exploited, this flaw can cause a segmentation violation, potentially leading to information disclosure or application crashes.

Critical Impact

This out-of-bounds read vulnerability in the widely-used ncurses terminfo library can result in unauthorized memory access and denial of service through segmentation faults, affecting multiple operating systems including macOS and Debian Linux.

Affected Products

• GNU ncurses versions prior to 6.3 patch 20220416
• Apple macOS (affected versions addressed in HT213488)
• Debian Linux 10.0

Discovery Timeline

• 2022-04-18 - CVE-2022-29458 published to NVD
• 2025-06-09 - Last updated in NVD database

Technical Details for CVE-2022-29458

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-Bounds Read), a memory safety issue that occurs when a program reads data past the boundary of an allocated buffer. The flaw resides specifically in the convert_strings function within the terminfo library component of ncurses.

The terminfo library is responsible for providing a terminal-independent method for accessing terminal capabilities. When processing malformed or specially crafted terminfo database entries, the convert_strings function fails to properly validate buffer boundaries, resulting in an out-of-bounds read operation. This memory access violation triggers a segmentation fault, causing the application to crash.

The vulnerability requires local access and some level of user interaction to exploit, as an attacker would need to introduce a malicious terminfo entry that gets processed by an application using the ncurses library.

Root Cause

The root cause of CVE-2022-29458 lies in insufficient bounds checking within the convert_strings function in tinfo/read_entry.c. The function processes string data from terminfo entries without adequately validating that read operations remain within the allocated buffer boundaries. When the function encounters malformed input data, it attempts to read beyond the buffer's allocated memory space, triggering an out-of-bounds read condition.

Attack Vector

The attack vector for this vulnerability is local, meaning an attacker requires access to the target system to exploit it. Exploitation typically involves:

1. Crafting a malicious terminfo database entry with malformed string data
2. Placing this entry where it will be processed by applications using the ncurses library
3. Triggering an application to parse the malicious terminfo entry, causing the out-of-bounds read

The vulnerability can lead to information disclosure if sensitive memory contents are leaked, or denial of service through application crashes caused by segmentation violations. For detailed technical information about the vulnerability mechanism, refer to the GNU Bug Report.

Detection Methods for CVE-2022-29458

Indicators of Compromise

• Unexpected segmentation faults or crashes in applications utilizing the ncurses library
• Abnormal terminfo database files or entries in /usr/share/terminfo/ or user-specific terminfo directories
• Application logs showing memory access violations related to terminfo parsing
• Unusual file modifications in terminfo database locations

Detection Strategies

• Monitor system logs for segmentation fault signals (SIGSEGV) in applications linked against ncurses
• Implement file integrity monitoring on terminfo database directories
• Use memory sanitizers (AddressSanitizer, Valgrind) during application testing to detect out-of-bounds reads
• Deploy endpoint detection and response (EDR) solutions capable of detecting memory access anomalies

Monitoring Recommendations

• Enable crash reporting and analysis for applications using the ncurses library
• Implement centralized logging to correlate potential exploitation attempts across systems
• Monitor for unauthorized modifications to terminfo database files
• Track package versions to identify systems running vulnerable ncurses versions

How to Mitigate CVE-2022-29458

Immediate Actions Required

• Update ncurses to version 6.3 with patch 20220416 or later immediately
• For Apple macOS systems, apply the security update referenced in Apple Support Article HT213488
• For Debian Linux systems, apply updates as detailed in the Debian LTS Security Announcement
• Inventory all systems running applications that depend on the ncurses library
• Prioritize patching for systems where untrusted users may be able to introduce custom terminfo entries

Patch Information

GNU has released patch 20220416 for ncurses 6.3 that addresses this vulnerability. The fix implements proper bounds checking in the convert_strings function to prevent out-of-bounds read operations. Vendor-specific patches are available from:

• GNU ncurses Bug Report - Original patch information
• Apple Security Updates - macOS security update
• Debian Security Advisory - Debian Linux packages

Workarounds

• Restrict write access to terminfo database directories to trusted administrators only
• Disable user-specific terminfo directories where possible by restricting TERMINFO environment variable
• Implement application sandboxing to limit the impact of potential crashes
• Consider using static terminfo configurations in controlled environments

# Verify ncurses version and check for vulnerability
ncurses6-config --version

# Restrict terminfo directory permissions (Linux/Unix)
chmod 755 /usr/share/terminfo
chmod 755 /lib/terminfo

# Disable user-specific terminfo in shell profiles
# Add to /etc/profile or user shell configuration
unset TERMINFO