CVE-2017-10684 in ncurses
Summary
by MITRE
In ncurses 6.0, there is a stack-based buffer overflow 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-2017-10684 represents a critical stack-based buffer overflow within the ncurses library version 6.0, specifically within the fmt_entry function. This flaw exists in the terminal handling and display capabilities of Unix-like systems, where ncurses serves as a foundational library for text-based user interfaces. The vulnerability arises from insufficient bounds checking when processing formatted input strings, creating a condition where maliciously crafted input can overwrite adjacent memory on the stack. The affected function processes terminal capability descriptions and formatting entries, making it a prime target for exploitation in environments where ncurses is utilized for user interface rendering or terminal emulation. Attackers can leverage this vulnerability to execute arbitrary code remotely by providing specially crafted input that triggers the buffer overflow during the formatting process.
The technical implementation of this vulnerability stems from improper input validation within the fmt_entry function, which handles formatted terminal capability entries. When the library processes terminal descriptions containing maliciously constructed format strings, the function fails to properly validate the length of input data against the allocated stack buffer size. This creates a classic stack buffer overflow condition where the program writes beyond the bounds of the allocated memory region, potentially overwriting return addresses, function pointers, or other critical stack data. The vulnerability is particularly dangerous because it can be triggered through terminal capability descriptions that are commonly loaded from configuration files or network sources, making remote exploitation feasible without requiring local system access. The flaw aligns with CWE-121 Stack-based Buffer Overflow, which specifically addresses buffer overflows occurring in stack memory regions.
The operational impact of CVE-2017-10684 extends beyond simple code execution, as it enables attackers to gain full control over affected systems running vulnerable versions of ncurses. This vulnerability affects a wide range of Unix and Linux systems where terminal interfaces are used, including servers, desktop environments, and embedded systems that rely on ncurses for user interaction. The remote exploitation capability means that attackers can compromise systems through network-based attacks, potentially leading to complete system takeover, data exfiltration, or persistence mechanisms. The vulnerability affects applications that utilize ncurses for displaying text-based interfaces, including various system administration tools, terminal emulators, and network services that depend on terminal capability handling. The impact is particularly severe in enterprise environments where terminal-based applications are prevalent, as a single compromised system could potentially provide attackers with access to broader network resources.
Mitigation strategies for CVE-2017-10684 focus primarily on updating to patched versions of the ncurses library, specifically versions 6.0 patch 20170826 or later. System administrators should prioritize patching all affected systems and applications that utilize ncurses, particularly those handling untrusted terminal capability descriptions or user input. Additionally, implementing input validation measures can help reduce the attack surface, though complete protection requires the library update. The vulnerability demonstrates the importance of proper bounds checking in C/C++ applications, aligning with ATT&CK technique T1059.007 for Command and Scripting Interpreter, where attackers may exploit such vulnerabilities to execute malicious code. Organizations should also consider network segmentation and monitoring for suspicious terminal capability loading activities, as well as implementing application whitelisting policies for terminal-based applications that interface with ncurses. Regular vulnerability assessments and security audits should include checks for ncurses versions and proper input handling within terminal applications to prevent exploitation of similar buffer overflow vulnerabilities.