CVE-2017-13731 in ncurses
Summary
by MITRE
There is an illegal address access in the function postprocess_termcap() in parse_entry.c in ncurses 6.0 that will lead to a remote denial of service attack.
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Analysis
by VulDB Data Team • 01/10/2021
The vulnerability identified as CVE-2017-13731 represents a critical security flaw within the ncurses library version 6.0, specifically within the postprocess_termcap() function located in parse_entry.c. This issue manifests as an illegal address access condition that can be exploited to execute a remote denial of service attack against systems utilizing affected ncurses implementations. The ncurses library serves as a fundamental component for terminal handling and text-based user interfaces across numerous Unix-like operating systems and applications, making this vulnerability particularly concerning for system stability and availability.
The technical nature of this flaw stems from improper memory management within the postprocess_termcap() function, where the code fails to adequately validate memory addresses before accessing them during terminal capability parsing operations. This vulnerability falls under the category of improper access to memory resources, which is classified as CWE-476 in the Common Weakness Enumeration catalog. The flaw occurs when the function processes terminal capability entries, particularly when handling malformed or specially crafted terminal descriptions that trigger unexpected memory access patterns. Attackers can exploit this by sending malicious terminal capability data to applications that rely on ncurses for terminal handling, potentially causing the target application to crash or become unresponsive.
The operational impact of CVE-2017-13731 extends beyond simple service disruption, as it can affect a wide range of applications and systems that depend on ncurses for terminal interface functionality. This includes but is not limited to shell environments, text editors, system monitoring tools, and various network applications that utilize terminal capabilities for user interaction. The remote nature of the attack means that adversaries can potentially exploit this vulnerability from outside the network perimeter, making it particularly dangerous for network services and applications accessible over the internet. Systems running vulnerable versions of ncurses are at risk of experiencing complete service outages, especially in environments where terminal handling is critical for system operations or user interaction.
Mitigation strategies for this vulnerability require immediate patching of affected ncurses installations to version 6.0 patch 20170826 or later, which contains the necessary fixes for the memory access issue. Organizations should conduct comprehensive inventory assessments to identify all systems utilizing vulnerable ncurses versions and prioritize patch deployment across their infrastructure. Network segmentation and access controls should be implemented to limit exposure of vulnerable applications to untrusted networks. Additionally, implementing proper input validation and sanitization measures for terminal capability data can provide additional defense-in-depth layers. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique for network denial of service and T1068 for local privilege escalation opportunities, highlighting the need for comprehensive security measures beyond simple patching to address the broader threat landscape.