CVE-2017-11112 in ncurses
Summary
by MITRE
In ncurses 6.0, there is an attempted 0xffffffffffffffff access in the append_acs function of tinfo/parse_entry.c. It could lead to a remote denial of service attack if the terminfo library code is used to process untrusted terminfo data.
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Analysis
by VulDB Data Team • 10/24/2019
The vulnerability identified as CVE-2017-11112 affects the ncurses library version 6.0, specifically within the terminfo processing functionality. This issue manifests in the append_acs function located in tinfo/parse_entry.c, where an attempted memory access operation targets an address that exceeds the valid range of the system's address space. The flaw represents a classic buffer over-read condition that occurs when processing untrusted terminfo data structures, which are used by terminal emulators and applications to determine terminal capabilities and behaviors.
The technical implementation of this vulnerability stems from improper bounds checking within the terminfo parsing routine. When ncurses encounters terminfo data containing malformed or maliciously crafted entries, the append_acs function attempts to access memory locations beyond the allocated buffer boundaries. The specific address value of 0xffffffffffffffff represents the maximum signed 64-bit integer, which when interpreted as a memory address, would naturally exceed the valid addressable range of typical systems. This improper memory access pattern can cause the application to crash or behave unpredictably when processing untrusted input through the terminfo subsystem.
From an operational perspective, this vulnerability creates a significant remote denial of service risk for systems that utilize ncurses for terminal handling and display management. Attackers could potentially craft malicious terminfo data that, when processed by applications using ncurses, would trigger the out-of-bounds memory access and cause the target application to terminate unexpectedly. This affects not only standalone applications but also systems that rely on terminal capabilities for user interaction, such as terminal emulators, text editors, and network applications that depend on proper terminal information for display formatting.
The impact extends beyond simple service disruption as this vulnerability could be exploited in environments where applications process terminal information from untrusted sources, including network services, terminal multiplexers, and applications that dynamically configure terminal behavior based on user-provided or remote terminal descriptions. Organizations using ncurses in production environments should be particularly concerned about this vulnerability as it could be leveraged to create persistent denial of service conditions against terminal-based services and applications.
Mitigation strategies should focus on immediate patching of affected ncurses versions to address the bounds checking issue in the append_acs function. System administrators should also implement input validation measures to prevent untrusted terminfo data from being processed by applications that utilize ncurses. Additionally, organizations should consider implementing sandboxing or containment strategies for applications that handle terminal information from external sources, ensuring that even if exploitation occurs, the impact remains limited. The vulnerability aligns with CWE-129, which addresses improper validation of array indices, and could potentially be mapped to ATT&CK technique T1059 for remote code execution through application vulnerabilities, though the current manifestation is primarily focused on denial of service rather than arbitrary code execution.