The vulnerability stems from Penelope Shell Handler’s download function on Unix, which uses tar.extractall on archives received from remote sessions without validating member paths. This allows a crafted archive to contain entries that resolve to locations outside the designated download directory, enabling an attacker who has the ability to supply the archive to write or overwrite files such as ~/.penelope/peneloperc.

The flaw affects the Brightio Penelope Shell Handler for authorized security testing. Any release older than 0.20.0 is affected. The issue was remedied starting with version 0.20.0, which incorporates validation of tar entry paths.

The CVSS score of 5.9 indicates moderate severity, and the EPSS score of less than 1% suggests that exploitation is currently very unlikely. The vulnerability is local and requires an attacker who can influence the content of a tar archive delivered by a remote session. Once exploited, it can overwrite configuration files or introduce arbitrary files, potentially enabling further privilege escalation or tampering with Penelope’s operation. The vulnerability is not listed in CISA’s KEV catalog.