CVE-2026-50558 in penelope
Summary
by MITRE • 07/29/2026
Penelope Shell Handler is a post-exploitation shell handler for authorized security testing. Prior to 0.20.0, the Unix download() implementation in penelope.py used tar.extractall(local_download_folder) on tar archives returned by remote sessions without validating member paths, allowing a malicious or compromised session to write files outside the intended download directory and potentially overwrite ~/.penelope/peneloperc. This issue is fixed in version 0.20.0.
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Analysis
by VulDB Data Team • 07/29/2026
The Penelope Shell Handler represents a specialized post-exploitation tool designed for authorized security testing operations, providing analysts with capabilities to manage and control compromised systems remotely. This tool operates within the cybersecurity domain as part of legitimate penetration testing and red team activities, where authorized professionals assess system vulnerabilities through controlled exploitation scenarios. The vulnerability under discussion specifically affects versions prior to 0200, highlighting a critical flaw in how the tool handles file extraction from remote tar archives during download operations.
The technical implementation flaw resides in the Unix download() function within the penelope.py module, which employs the tar.extractall() method without proper validation of member paths. This design decision creates a path traversal vulnerability where maliciously crafted tar archives can manipulate the extraction process to write files outside the designated local_download_folder directory. The absence of input sanitization allows attackers to specify arbitrary file paths within the tar archive that would result in file creation or modification beyond the intended download scope.
This vulnerability presents significant operational risks for security professionals using Penelope Shell Handler, as it could enable malicious actors who have compromised a session to execute privilege escalation attacks. The potential for overwriting the ~/.penelope/peneloperc configuration file represents a particularly concerning attack vector, since this file likely contains critical authentication credentials, session configurations, or other sensitive operational data. Such an attack could compromise the integrity of the entire testing environment and potentially provide attackers with persistent access to the security testing infrastructure.
The fix implemented in version 0200 addresses this vulnerability by introducing proper path validation mechanisms before executing tar.extractall() operations. This remediation aligns with established cybersecurity best practices for preventing directory traversal attacks and follows the principle of least privilege by ensuring that extracted files remain confined to their intended directories. Organizations utilizing Penelope Shell Handler should prioritize immediate upgrade to version 0200 or later to protect against this exploitation vector, particularly in environments where the tool may be exposed to compromised or malicious sessions.
This vulnerability classifies under CWE-22 Path Traversal and aligns with ATT&CK technique T1059 Command and Scripting Interpreter, specifically targeting the execution of commands through shell manipulation. The remediation approach demonstrates proper input validation practices that should be implemented across similar security tools handling untrusted archive files. Security practitioners should consider this vulnerability as part of broader defensive measures against post-exploitation tool abuse and maintain vigilance in validating all external inputs before processing potentially malicious payloads.
The incident underscores the importance of implementing robust file extraction controls in security tools, particularly those designed for remote system manipulation. Organizations should conduct regular security assessments of their penetration testing tools to identify similar vulnerabilities that could be exploited by adversaries who gain access to compromised sessions. This vulnerability serves as a reminder that even authorized security tools require careful attention to input validation and privilege management when handling potentially malicious data from remote sources.
The fix implemented in version 0200 represents a critical security enhancement that aligns with industry standards for secure coding practices and demonstrates the importance of maintaining up-to-date security tooling. Security teams should establish processes for monitoring security advisories related to their penetration testing tools and ensure timely deployment of security patches to protect against known vulnerabilities that could compromise operational integrity or provide attackers with additional attack surface opportunities.