CVE-2017-10685 in ncurses
Summary
by MITRE
In ncurses 6.0, there is a format string vulnerability in the fmt_entry function. A crafted input will lead to a remote arbitrary code execution attack.
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Analysis
by VulDB Data Team • 10/21/2019
The vulnerability identified as CVE-2017-10685 resides within the ncurses library version 6.0, specifically within the fmt_entry function that handles formatted output operations. This format string vulnerability represents a critical security flaw that can be exploited to execute arbitrary code remotely. The ncurses library serves as a fundamental component for terminal handling and user interface creation in numerous Unix-like operating systems and applications, making this vulnerability particularly dangerous as it affects a widely deployed system library. The flaw manifests when the application processes user-supplied input through the fmt_entry function without proper validation or sanitization of format specifiers, creating an environment where malicious input can be interpreted as executable code rather than mere data.
Technical exploitation of this vulnerability occurs through manipulation of format string arguments that are passed to the fmt_entry function, allowing attackers to control the execution flow of affected applications. The vulnerability falls under CWE-134, which specifically addresses format string vulnerabilities where format specifiers in user-controlled input can be used to read from or write to arbitrary memory locations. When an attacker crafts malicious input containing format specifiers such as %x, %s, or %n, the vulnerable function processes these without proper bounds checking or input validation, potentially leading to stack corruption, information disclosure, or direct code execution. The attack vector typically involves applications that utilize ncurses for displaying formatted terminal output and accept untrusted input from external sources, making network services, terminal emulators, and system utilities prime targets for exploitation.
The operational impact of CVE-2017-10685 extends far beyond individual application compromise, as the ncurses library is integral to countless system components and user interfaces across various operating systems. Attackers can leverage this vulnerability to escalate privileges, gain unauthorized access to systems, or establish persistent backdoors through remote code execution capabilities. The vulnerability's severity is amplified by the fact that many system-level applications and services depend on ncurses for their terminal interface functionality, meaning that exploitation could affect critical infrastructure components including shell utilities, system monitoring tools, and network services. Additionally, the vulnerability can be exploited through various attack vectors including network-based attacks, file upload scenarios, or command-line argument injection, making it particularly challenging to defend against comprehensively. Organizations running systems with vulnerable ncurses versions face significant risk of complete system compromise, as the vulnerability allows for arbitrary code execution that can bypass standard security controls and access protected system resources.
Mitigation strategies for CVE-2017-10685 primarily focus on updating to patched versions of the ncurses library, specifically versions 6.0 through 6.1 which contain the necessary fixes for the format string vulnerability. System administrators should prioritize patching affected systems and applications that utilize ncurses, particularly those handling untrusted input through terminal interfaces. Additional defensive measures include implementing input validation and sanitization for all user-supplied data, using address space layout randomization to complicate exploitation attempts, and employing stack canaries to detect potential stack corruption. Network segmentation and access controls should be implemented to limit exposure of vulnerable applications to untrusted networks or users. Security monitoring should include detection of anomalous format string usage patterns and unusual memory access behaviors that might indicate exploitation attempts. Organizations should also consider implementing the principle of least privilege for applications using ncurses, limiting their capabilities and access rights to reduce potential damage from successful exploitation attempts. The vulnerability's classification under ATT&CK technique T1059.007 for command and scripting interpreter indicates that exploitation could lead to lateral movement and persistent access within compromised environments, further emphasizing the need for comprehensive mitigation strategies.