CVE-2026-66486 in Cpio
Summary
by MITRE • 08/10/2026
GNU cpio is vulnerable to improper encoding or escaping of output in its archive member listing functionality. When listing archive members via cpio -it, member names are printed directly to output without quoting or escaping. An attacker can craft a cpio archive containing member names with embedded newline characters or ANSI escape sequences, causing forged listing entries or terminal control sequence injection when the listing is displayed.
This issue has been fixed in commit 2ff9600c9ef32e88759843cdbde74c8db5ae9b30
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability in GNU cpio affects the archive member listing functionality where the tool fails to properly escape or quote output when displaying archive contents through commands such as cpio -it. This flaw represents a classic case of improper input handling that can lead to serious security implications within terminal environments. The core technical issue lies in how cpio processes and outputs member names without implementing appropriate sanitization measures, creating opportunities for malicious actors to manipulate the display behavior of the tool.
When archive members contain specially crafted filenames with embedded newline characters or ANSI escape sequences, the lack of proper output encoding allows these control characters to be interpreted by terminal emulators during display. This creates a scenario where an attacker can inject terminal control sequences that modify the display behavior, potentially leading to misleading information presentation or even command injection in certain contexts. The vulnerability directly maps to CWE-15 improper neutralization of special elements used in output contexts, specifically manifesting as inadequate output escaping in command line tools.
The operational impact of this vulnerability extends beyond simple display manipulation to potential security escalation opportunities within environments where cpio is used for archive inspection. When users view archive contents through cpio listings, they may inadvertently execute terminal commands or be presented with misleading information that could deceive them into making incorrect decisions about the archive contents. This becomes particularly dangerous in automated systems or when cpio output is processed by other tools without proper sanitization, creating cascading security implications.
The fix implemented in commit 2ff9600c9ef32e88759843cdbde74c8db5ae9b30 addresses the root cause by ensuring that archive member names are properly quoted or escaped before being output to terminal displays. This solution aligns with security best practices for command line tool development and follows ATT&CK framework techniques related to input validation and output encoding. The mitigation approach prevents malicious filenames from containing control characters that could influence terminal behavior, thereby protecting users from potential deception or injection attacks. Security practitioners should ensure that all versions of GNU cpio are updated to include this fix to prevent exploitation of this vulnerability in production environments where archive inspection occurs.
This vulnerability demonstrates the importance of proper output handling in security-critical tools and highlights how seemingly benign functionality can become a vector for attack when input validation is insufficient. The issue serves as a reminder that command line utilities processing user-provided data must implement robust sanitization measures to prevent control character injection attacks that could compromise system integrity or user trust in displayed information.