CVE-2017-13733 in ncurses
Summary
by MITRE
There is an illegal address access in the fmt_entry function in progs/dump_entry.c in ncurses 6.0 that might 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-2017-13733 resides within the ncurses library version 6.0, specifically in the fmt_entry function located in progs/dump_entry.c. This flaw represents a critical security issue that could potentially enable remote attackers to disrupt system operations through a carefully crafted input sequence. The ncurses library serves as a fundamental component for terminal handling and user interface development across numerous Unix-like operating systems, making this vulnerability particularly concerning given its widespread adoption. The issue manifests as an illegal address access condition that occurs during the processing of formatted terminal entries, creating a potential pathway for denial of service attacks that could compromise system availability.
The technical implementation of this vulnerability stems from improper bounds checking within the fmt_entry function's handling of input data structures. When the function processes terminal entry information, it fails to adequately validate memory access patterns, leading to potential buffer overread or invalid memory dereference scenarios. This type of flaw falls under the CWE-125 vulnerability category, which describes out-of-bounds read conditions that can result in information disclosure, system crashes, or potentially more severe exploitation outcomes. The improper handling of input parameters during the formatting process creates a scenario where maliciously constructed terminal entry data could trigger the illegal address access, causing the application to terminate unexpectedly or behave unpredictably.
From an operational perspective, this vulnerability presents significant risks to system administrators and security teams responsible for maintaining terminal-based applications and services. The remote denial of service capability means that attackers could potentially disrupt critical terminal operations without requiring local access or elevated privileges. Systems that rely heavily on ncurses for command-line interfaces, text-based user interfaces, or terminal emulators would be particularly vulnerable to this attack vector. The impact extends beyond simple service disruption as the vulnerability could affect various applications including system monitoring tools, configuration utilities, and network management applications that depend on ncurses functionality. This vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through exploitation of software vulnerabilities.
The mitigation strategies for CVE-2017-13733 primarily involve immediate patching of affected systems with updated versions of the ncurses library that address the bounds checking deficiencies. System administrators should prioritize updating all instances of ncurses 6.0 to versions that contain the necessary fixes for this vulnerability. Additionally, implementing network segmentation and access controls can help limit potential attack surfaces by restricting unauthorized access to systems that utilize vulnerable ncurses functionality. Monitoring network traffic for suspicious patterns related to terminal entry processing may also aid in detecting potential exploitation attempts. Organizations should also consider implementing application-level sandboxing for applications that process external terminal data to limit the potential impact of successful exploitation attempts. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date system libraries and the potential consequences of failing to address known security flaws in foundational software components.