CVE-2000-0963 in ncurses
Summary
by MITRE
Buffer overflow in ncurses library allows local users to execute arbitrary commands via long environmental information such as TERM or TERMINFO_DIRS.
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Analysis
by VulDB Data Team • 08/26/2019
The vulnerability identified as CVE-2000-0963 represents a critical buffer overflow flaw within the ncurses library, a fundamental component used for terminal handling and user interface programming in Unix-like operating systems. This library serves as the foundation for numerous applications including screen managers, text editors, and system utilities that require terminal-based user interaction. The flaw specifically manifests when the library processes environmental variables, particularly TERM and TERMINFO_DIRS, which define terminal type and location of terminal information files respectively. The buffer overflow occurs because the ncurses library fails to properly validate the length of these environmental variables before copying them into fixed-size buffers, creating a condition where maliciously crafted input can overwrite adjacent memory locations.
The technical implementation of this vulnerability exploits the inherent design flaw in how ncurses handles environmental variable processing. When applications utilizing ncurses initialize their terminal environment, they rely on the TERM variable to determine terminal capabilities and the TERMINFO_DIRS variable to locate terminal description files. Attackers can craft overly long values for these variables, typically exceeding the allocated buffer space, which results in memory corruption that can be leveraged to execute arbitrary code with the privileges of the affected process. This exploitation vector is particularly dangerous because it operates at the library level, meaning any application linking against ncurses could potentially be compromised. The vulnerability falls under the CWE-121 category of Stack-based Buffer Overflow, specifically manifesting as a classic buffer overrun where insufficient bounds checking allows data to overflow into adjacent memory regions.
The operational impact of CVE-2000-0963 extends beyond individual applications to potentially compromise entire system security postures, particularly in multi-user environments where local privilege escalation opportunities exist. Local users who can influence environmental variables can leverage this vulnerability to execute malicious code with elevated privileges, potentially leading to complete system compromise. The attack surface is broad since ncurses is integral to many system utilities and applications, making the exploitation potential widespread across different software packages. From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1068 which involves local privilege escalation through exploitation of software vulnerabilities. The impact is further amplified because the vulnerability can be exploited without requiring network connectivity, making it particularly insidious in environments where network-based defenses may be insufficient.
Mitigation strategies for this vulnerability require immediate patching of affected ncurses library versions, with the most effective approach being the installation of updated library versions that implement proper bounds checking for environmental variable processing. System administrators should also implement environmental variable validation at the application level, ensuring that terminal-related variables are properly sanitized before being processed by ncurses. Additional protective measures include implementing strict privilege separation for applications that utilize ncurses, employing runtime monitoring to detect anomalous buffer behavior, and conducting regular security audits of terminal-based applications. The vulnerability highlights the importance of secure coding practices in system libraries, particularly regarding input validation and memory management, and serves as a reminder of the critical nature of maintaining up-to-date system components to prevent exploitation of known vulnerabilities. Organizations should also consider implementing automated patch management systems to ensure timely remediation of similar issues across their infrastructure.