CVE-2023-50495: Ncurse Buffer Overflow Vulnerability

CVE-2023-50495 Overview

NCurses v6.4-20230418 was discovered to contain a segmentation fault vulnerability via the component _nc_wrap_entry(). This vulnerability allows remote attackers to cause a denial of service condition through network-based attacks that require user interaction. The NCurses library is widely used across Unix-like operating systems for terminal handling and text-based user interfaces, making this vulnerability particularly significant for systems relying on terminal-based applications.

Critical Impact

A successful exploitation of this vulnerability can result in application crashes and denial of service conditions, impacting the availability of systems and applications that depend on the NCurses library for terminal handling functionality.

Affected Products

• Invisible-island NCurses v6.4-20230418

Discovery Timeline

• April 2023 - Vulnerability reported via GNU NCurses bug tracking system
• 2023-12-12 - CVE-2023-50495 published to NVD
• 2025-11-04 - Last updated in NVD database

Technical Details for CVE-2023-50495

Vulnerability Analysis

This vulnerability is classified as a Denial of Service issue stemming from a segmentation fault in the NCurses library. The flaw exists within the _nc_wrap_entry() function, which is responsible for handling terminal capability entries. When processing specially crafted input, the function fails to properly validate memory access boundaries, resulting in a segmentation fault that terminates the affected application.

The vulnerability requires network access and user interaction to exploit. An attacker could craft malicious terminal data or terminfo entries that, when processed by an application using the vulnerable NCurses library, triggers the segmentation fault in _nc_wrap_entry(). While this vulnerability does not allow for code execution or data exfiltration, it effectively disrupts service availability.

Root Cause

The root cause of CVE-2023-50495 lies in improper memory handling within the _nc_wrap_entry() function. The function fails to adequately validate pointers or array boundaries before accessing memory, leading to a null pointer dereference or out-of-bounds memory access when processing certain terminal capability entries. This results in a segmentation fault (SIGSEGV) signal being raised by the operating system, immediately terminating the affected process.

Attack Vector

The attack vector for this vulnerability is network-based but requires user interaction. An attacker can exploit this vulnerability through several potential scenarios:

1. Malicious Terminfo Entries: Crafting malicious terminfo database entries that trigger the vulnerability when an application attempts to initialize terminal handling
2. Crafted Terminal Input: Sending specially crafted escape sequences or terminal data to applications using NCurses for terminal I/O
3. Malicious Configuration Files: Providing malformed configuration that references or includes data triggering the vulnerable code path

The vulnerability manifests in the _nc_wrap_entry() function when processing terminal capability entries. The function does not properly handle edge cases in entry wrapping, leading to memory access violations. For detailed technical analysis, refer to the GNU Ncurses Bug Report.

Detection Methods for CVE-2023-50495

Indicators of Compromise

• Unexpected application crashes with segmentation fault (SIGSEGV) signals in NCurses-dependent applications
• Core dumps showing crash traces originating from _nc_wrap_entry() or related NCurses functions
• Repeated service restarts for terminal-based applications without apparent cause
• System logs indicating abnormal termination of processes using libncurses

Detection Strategies

• Monitor system logs for SIGSEGV signals in processes linked against NCurses libraries
• Implement application crash monitoring and alerting for NCurses-dependent services
• Use software composition analysis (SCA) tools to identify systems running vulnerable NCurses version 6.4-20230418
• Deploy endpoint detection solutions capable of identifying abnormal process termination patterns

Monitoring Recommendations

• Configure centralized logging to capture application crash events and core dump generation
• Implement process monitoring for critical terminal-based applications to detect unexpected terminations
• Use SentinelOne Singularity platform to monitor for abnormal process behavior and crash patterns
• Establish baseline metrics for application availability to quickly identify denial of service conditions

How to Mitigate CVE-2023-50495

Immediate Actions Required

• Inventory all systems using NCurses library version 6.4-20230418
• Update NCurses to the latest patched version available from your distribution's package repository
• Review and apply vendor-specific patches as referenced in the Fedora Package Announcement
• Consult the NetApp Security Advisory if using affected NetApp products

Patch Information

Patches for this vulnerability are available through standard distribution channels. Fedora has released updated packages addressing this issue. System administrators should consult their respective distribution's security advisories and apply updates through standard package management procedures.

For additional context and patch details, refer to the GNU Ncurses bug tracking discussions which contain technical details about the fix.

Workarounds

• Implement process supervision and automatic restart mechanisms for critical NCurses-dependent applications to minimize downtime
• Restrict network exposure of vulnerable terminal-based applications where feasible
• Consider containerizing affected applications to limit the impact of crashes
• Apply defense-in-depth measures by limiting user interaction with potentially malicious terminal data sources

# Check installed NCurses version on Debian/Ubuntu systems
dpkg -l | grep ncurses

# Check installed NCurses version on RHEL/CentOS/Fedora systems
rpm -qa | grep ncurses

# Update NCurses on Debian/Ubuntu
sudo apt update && sudo apt upgrade libncurses*

# Update NCurses on Fedora
sudo dnf update ncurses