CVE-2026-49147 in App::Ack
Summary
by MITRE • 07/08/2026
App::Ack versions through 3.10.0 for Perl print unsanitised terminal escape sequences from filenames in several output modes.
When ack prints a filename whose basename contains terminal control bytes such as ANSI escape sequences, those bytes reach the terminal unchanged. Version 3.10.0 added a _safe_filename helper that sanitises the filenames printed by -f, -g, the colored match heading, and per-match lines, but the --show-types, -l/-L, and -c paths still emit the raw filename.
A file whose name embeds cursor-movement or color escapes can overwrite or recolor earlier terminal output, or be passed unchanged to a downstream consumer.
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Analysis
by VulDB Data Team • 07/08/2026
The vulnerability in App::Ack versions through 3.10.0 represents a serious security flaw that enables maliciously crafted filenames to execute arbitrary terminal commands through embedded control sequences. This issue stems from insufficient input sanitization when displaying filenames containing terminal escape sequences, creating an environment where attackers can manipulate terminal output behavior. The vulnerability specifically affects the display of filenames in various output modes including --show-types, -l/-L, and -c flags, where raw filename content is passed directly to terminal without proper sanitization. This creates a potential vector for terminal-based attacks that could be exploited in environments where ack is used with untrusted input or when users encounter files with specially crafted names.
The technical implementation of this vulnerability involves the improper handling of terminal control sequences within filename strings during output processing. When ack encounters filenames containing ANSI escape codes or other terminal control bytes, these sequences are passed directly to the terminal without sanitization, allowing them to execute their intended terminal commands. The _safe_filename helper function introduced in version 3.10.0 only addresses a subset of output modes, leaving several critical paths unsecured. This partial fix demonstrates a flawed approach to security remediation where only some code paths receive proper sanitization while others remain vulnerable, creating an inconsistent security posture that attackers can exploit by targeting the unprotected paths.
The operational impact of this vulnerability extends beyond simple terminal manipulation to potentially enable more sophisticated attacks depending on the execution environment. An attacker could craft filenames containing cursor movement sequences that overwrite existing terminal output, making it appear as though legitimate command results have been altered or hidden. Color manipulation sequences could be used to make certain output invisible or misleading, creating confusion during security audits or routine operations. In more severe scenarios, when ack output is processed by downstream tools or scripts, the unsanitized escape sequences could propagate into those systems, potentially enabling injection attacks against automated processing pipelines. This vulnerability aligns with CWE-74 and CWE-150 categories related to improper neutralization of special elements in output used by a downstream component.
The security implications become particularly concerning when considering how ack is typically used in development environments where it processes large numbers of files from potentially untrusted sources. When developers encounter files with specially crafted names containing terminal escape sequences, the vulnerability can be exploited to manipulate console output during code reviews, debugging sessions, or automated build processes. This opens potential attack vectors for privilege escalation scenarios where an attacker might use the terminal manipulation capabilities to hide malicious file discoveries or alter the appearance of legitimate security tools' outputs. The vulnerability also aligns with ATT&CK techniques related to terminal manipulation and output injection, providing attackers with methods to obscure their activities within command-line environments.
Effective mitigation strategies should focus on implementing comprehensive filename sanitization across all output modes in ack. The most appropriate solution involves extending the _safe_filename helper function to cover all code paths that display filenames, ensuring consistent handling of control sequences regardless of output mode. System administrators and security teams should consider updating to version 3.10.1 or later where this vulnerability has been addressed through complete sanitization of filename display across all modes. Organizations using ack in automated environments should implement additional input validation measures, particularly when processing files from untrusted sources, and consider logging or monitoring for unusual terminal control sequence patterns in filenames. The remediation approach should follow security best practices outlined in industry standards such as OWASP's input validation guidelines and NIST cybersecurity frameworks that emphasize the importance of sanitizing all user-provided data before display to prevent injection-based attacks.