CVE-2017-13732 in ncurses
Summary
by MITRE
There is an illegal address access in the function dump_uses() 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-2017-13732 represents a critical flaw in the ncurses library version 6.0, specifically within the dump_uses() function located in progs/dump_entry.c. This issue manifests as an illegal address access condition that can be exploited to execute remote denial of service attacks. The ncurses library serves as a fundamental component for terminal handling and screen rendering in numerous Unix-like operating systems and applications, making this vulnerability particularly concerning from a security perspective. The flaw occurs during the processing of terminal entries and dump operations, where improper memory access patterns can lead to system instability and service disruption.
The technical root cause of this vulnerability stems from inadequate bounds checking and memory validation within the dump_uses() function. When the function processes terminal capability data, it fails to properly validate array indices or memory pointers before accessing allocated memory regions. This improper validation creates an opportunity for attackers to craft malicious input that triggers unauthorized memory access patterns. The vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and CWE-787, which covers out-of-bounds write vulnerabilities. These weakness categories specifically address improper bounds checking that allows attackers to access memory locations outside the intended buffer boundaries.
From an operational standpoint, this vulnerability presents a significant risk to systems relying on ncurses for terminal operations, including but not limited to shell environments, text editors, system monitoring tools, and network management applications. The remote denial of service aspect means that attackers can potentially disrupt services without requiring local access or authentication. Attackers can exploit this by sending specially crafted terminal capability data or terminal entries that cause the dump_uses() function to access invalid memory addresses. The impact extends beyond individual applications to potentially affect entire system services that depend on proper terminal handling functionality. This vulnerability can be particularly dangerous in server environments where terminal-based services are prevalent.
The exploitation of CVE-2017-13732 can be mapped to several ATT&CK techniques including T1499, which involves network disruption attacks, and T1059, which covers command and scripting interpreter usage. The vulnerability can be leveraged through command injection or manipulation of terminal entry files that are processed by ncurses applications. Security practitioners should consider this vulnerability in their threat modeling and incident response planning, particularly for systems running vulnerable versions of ncurses. The vulnerability's classification as a denial of service attack means that mitigation strategies should focus on preventing unauthorized access to terminal processing functions and implementing proper input validation mechanisms. Organizations should prioritize patching their ncurses installations to version 6.1 or later, where this vulnerability has been addressed through improved memory access validation and bounds checking procedures.
This vulnerability demonstrates the critical importance of proper memory management in system libraries that handle user input or external data processing. The flaw represents a classic example of how seemingly minor issues in low-level system components can have widespread implications for system security and availability. The remediation efforts should include comprehensive testing of patched versions to ensure that no regressions have been introduced and that the fix properly addresses the memory access violations without impacting legitimate functionality. Additionally, organizations should implement monitoring for unusual terminal processing activities that might indicate exploitation attempts, particularly in environments where terminal-based applications are prevalent.