CVE-2017-13734 in ncurses
Summary
by MITRE
There is an illegal address access in the _nc_safe_strcat function in strings.c in ncurses 6.0 that will lead to a remote denial of service attack.
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Analysis
by VulDB Data Team • 11/11/2019
The vulnerability identified as CVE-2017-13734 resides within the ncurses library version 6.0, specifically in the _nc_safe_strcat function located in the strings.c file. This flaw represents a critical security issue that can be exploited to execute remote denial of service attacks. The ncurses library serves as a fundamental component for terminal handling and text-based user interfaces across numerous Unix-like operating systems and applications. When applications utilize ncurses for terminal management, they become susceptible to this vulnerability if they process untrusted input through the affected string concatenation function.
The technical root cause of this vulnerability stems from improper bounds checking within the _nc_safe_strcat function, which is designed to safely concatenate strings while preventing buffer overflows. However, the implementation contains a flaw that allows for illegal address access when handling certain input sequences. This occurs during string manipulation operations where the function fails to properly validate the length of source strings before attempting concatenation. The vulnerability manifests when malicious input is processed through the vulnerable code path, causing the function to access memory locations outside of its intended bounds, leading to unpredictable behavior and system instability.
From an operational impact perspective, this vulnerability poses significant risks to systems that rely on ncurses for terminal interface management. Applications including but not limited to terminal emulators, text editors, system monitoring tools, and network management utilities may become vulnerable to remote denial of service attacks. Attackers can craft specific input sequences that trigger the illegal address access, potentially causing applications to crash or become unresponsive. The remote nature of this attack means that adversaries can exploit the vulnerability without requiring local access to the target system, making it particularly dangerous in networked environments. The vulnerability affects a wide range of systems since ncurses is a widely deployed library across various Unix and Linux distributions, making it a prime target for exploitation.
The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and more specifically relates to improper input validation in string handling operations. From an attack framework perspective, this vulnerability can be categorized under the ATT&CK technique T1499.004, which involves network denial of service attacks, and potentially T1059.007 for command and scripting interpreter usage in exploitation contexts. The flaw demonstrates the critical importance of proper memory management and input validation in system libraries, as even widely trusted components can contain vulnerabilities that affect entire ecosystems. Organizations should prioritize patching this vulnerability through updates to ncurses library versions that contain fixed implementations of the _nc_safe_strcat function, ensuring that proper bounds checking mechanisms are in place to prevent unauthorized memory access patterns and maintain system stability and availability.