CVE-2017-13729 in ncurses
Summary
by MITRE
There is an illegal address access in the _nc_save_str function in alloc_entry.c in ncurses 6.0. It 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-2017-13729 represents a critical memory access issue within the ncurses library version 6.0, specifically within the _nc_save_str function located in alloc_entry.c. This flaw manifests as an illegal address access condition that can be exploited to execute a remote denial of service attack against systems utilizing vulnerable 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 from a security perspective. The issue arises from improper bounds checking or memory management within the string allocation and saving mechanisms of the library, creating a scenario where malicious input can cause the application to attempt accessing memory locations outside of its allocated address space.
The technical implementation of this vulnerability stems from inadequate validation within the _nc_save_str function which processes string data during terminal interface operations. When the function encounters certain malformed or specially crafted input sequences, it fails to properly verify memory boundaries before attempting to store or manipulate string data. This improper memory handling creates a condition where the function may attempt to write to or read from invalid memory addresses, potentially causing application crashes or system instability. The vulnerability is classified under CWE-125 as an "Out-of-Bounds Read" or potentially CWE-787 as an "Out-of-Bounds Write" depending on the specific execution path taken during exploitation. The remote nature of the denial of service attack means that an attacker can trigger this condition without requiring local access, simply by providing malicious input to any application that utilizes the vulnerable ncurses library.
From an operational impact standpoint, this vulnerability affects systems where ncurses is used as a dependency for terminal-based applications, which includes but is not limited to shell environments, text editors, system monitoring tools, and various network services that rely on terminal interface capabilities. The denial of service aspect can severely impact system availability and user experience, potentially causing applications to crash or become unresponsive, which may require system restarts or manual intervention to restore normal operations. Attackers can exploit this vulnerability to disrupt services by sending crafted input to applications that use ncurses, leading to cascading failures in terminal-based systems. The impact extends beyond individual applications to potentially affect entire system stability, especially in environments where multiple services depend on terminal handling capabilities. According to ATT&CK framework, this vulnerability aligns with T1499.004 which covers "Endpoint Denial of Service" and represents a technique that can be used to compromise system availability and maintain access by disrupting normal operations.
Mitigation strategies for CVE-2017-13729 primarily involve upgrading to a patched version of the ncurses library where the memory access issue has been resolved through proper bounds checking and input validation mechanisms. System administrators should prioritize updating their ncurses installations to version 6.1 or later, where the vulnerability has been addressed through enhanced memory management practices. Additionally, implementing proper input sanitization at application layers that utilize ncurses can provide an additional defense-in-depth measure. Organizations should also consider monitoring for exploitation attempts through log analysis and intrusion detection systems, particularly focusing on unusual input patterns that might indicate attempts to trigger this vulnerability. The patch implementation should include comprehensive testing to ensure that the fix does not introduce regressions in existing functionality while effectively addressing the memory access issue. Regular vulnerability assessments and security audits should be conducted to identify and remediate similar issues in other system components that may be susceptible to similar memory corruption vulnerabilities.