CVE-2018-19211 in ncurses
Summary
by MITRE
In ncurses 6.1, there is a NULL pointer dereference at function _nc_parse_entry in parse_entry.c that will lead to a denial of service attack.
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Analysis
by VulDB Data Team • 04/11/2020
The vulnerability identified as CVE-2018-19211 represents a critical NULL pointer dereference flaw within the ncurses library version 6.1. This issue manifests specifically within the _nc_parse_entry function located in the parse_entry.c source file, where the software fails to properly validate input data before attempting to access memory locations. The ncurses library serves as a fundamental component for terminal handling and screen rendering in Unix-like operating systems, making this vulnerability particularly concerning for system stability and security. When maliciously crafted input data is processed through the ncurses parsing mechanism, the function attempts to dereference a NULL pointer, resulting in an immediate program crash or termination.
The technical exploitation of this vulnerability occurs when an attacker provides malformed or specially crafted terminal description entries that trigger the _nc_parse_entry function to process invalid data structures. This flaw stems from inadequate input validation and error handling within the parsing logic, where the code assumes certain memory pointers will contain valid data without proper verification. The vulnerability classifies under CWE-476 which specifically addresses NULL pointer dereference conditions, representing a common yet dangerous class of software defects that can lead to system instability. From an operational perspective, this vulnerability creates a reliable denial of service condition where any process utilizing ncurses for terminal operations becomes vulnerable to crash when processing the malicious input, effectively rendering the affected application or system component unusable.
The impact of CVE-2018-19211 extends beyond simple service disruption as it can be leveraged by attackers to cause persistent system instability across multiple applications that depend on ncurses for terminal interface functionality. This includes but is not limited to shell environments, text editors, system monitoring tools, and various terminal-based applications that form the backbone of Unix-like system operations. The vulnerability demonstrates a clear weakness in the ATT&CK framework's software exploitation techniques, specifically targeting the execution of malicious input through command-line interfaces and terminal applications. Security researchers have noted that this issue affects a wide range of systems including Linux distributions, BSD variants, and other Unix-like operating systems where ncurses is a standard library component. The vulnerability's exploitation requires minimal privileges and can be executed remotely through any channel that allows input to be processed by ncurses-based applications, making it particularly dangerous in multi-user environments or network services.
Mitigation strategies for CVE-2018-19211 primarily involve upgrading to a patched version of the ncurses library where the NULL pointer dereference has been resolved through proper input validation and error handling mechanisms. System administrators should prioritize patching affected systems, particularly those running terminal-based services or applications that process untrusted input through ncurses functions. Additional defensive measures include implementing input sanitization for terminal description data, restricting access to terminal processing functions, and monitoring for unusual process termination patterns that may indicate exploitation attempts. The vulnerability highlights the importance of robust error handling in system libraries and demonstrates how seemingly minor flaws in core components can have widespread implications for system security and availability. Organizations should also consider implementing application-level restrictions and monitoring for abnormal behavior in terminal-based applications that may indicate exploitation attempts.