CVE-2017-16544 in N-Tron 702-W
Summary
by MITRE
In the add_match function in libbb/lineedit.c in BusyBox through 1.27.2, the tab autocomplete feature of the shell, used to get a list of filenames in a directory, does not sanitize filenames and results in executing any escape sequence in the terminal. This could potentially result in code execution, arbitrary file writes, or other attacks.
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Analysis
by VulDB Data Team • 06/09/2025
The vulnerability CVE-2017-16544 resides within the BusyBox project's line editing functionality, specifically in the add_match function located in libbb/lineedit.c. This flaw affects BusyBox versions through 1.27.2 and represents a critical security issue that exploits the shell's tab autocomplete feature. The vulnerability emerges from insufficient sanitization of filenames during directory listing operations, creating a pathway for malicious input to be interpreted as terminal escape sequences rather than simple file names. The tab completion mechanism, designed to enhance user experience by suggesting filenames, becomes a vector for privilege escalation and arbitrary code execution when confronted with specially crafted filenames containing escape sequences.
The technical implementation of this vulnerability stems from the improper handling of filename characters within the shell's interactive environment. When users invoke tab autocomplete, the system displays a list of matching filenames from the current directory, but the add_match function fails to properly sanitize these filenames before displaying them. This sanitization gap allows filenames containing ANSI escape sequences or other terminal control codes to be processed as actual terminal commands rather than literal file names. The vulnerability operates at the intersection of shell interaction and terminal protocol handling, where legitimate filename characters are misinterpreted as control sequences that can manipulate terminal state, cursor position, or even execute commands directly within the terminal environment.
The operational impact of CVE-2017-16544 extends beyond simple information disclosure to encompass potential code execution and system compromise. Attackers can craft filenames containing escape sequences that, when tab-completed, trigger unintended terminal behavior including command execution, file system modifications, or even privilege escalation within the shell environment. This vulnerability particularly affects systems running BusyBox versions where shell functionality is exposed to untrusted users, such as in embedded systems, containerized environments, or network services that utilize BusyBox utilities. The exploitability of this vulnerability aligns with ATT&CK technique T1059.006 for command and script injection, and CWE-74 for improper neutralization of special elements, making it a significant threat in environments where shell access is provided to potentially malicious users.
Mitigation strategies for CVE-2017-16544 primarily involve upgrading to BusyBox versions that contain the patched implementation of the add_match function. System administrators should prioritize updating their BusyBox installations to versions beyond 1.27.2 where the filename sanitization has been properly implemented. Additional defensive measures include restricting shell access for untrusted users, implementing proper input validation at the application level, and monitoring for suspicious terminal behavior patterns. The vulnerability demonstrates the importance of proper input sanitization in interactive shell environments and highlights how seemingly benign features like tab completion can become attack vectors when insufficiently validated. Organizations should also consider implementing terminal session monitoring to detect and prevent exploitation attempts targeting this specific vulnerability pattern.