Deserialization of untrusted data in the report-processing code of Puppet, as used by Puppet Server, allows a client with any CA‑signed agent certificate to execute arbitrary code on the Puppet Server as its service user by submitting a report containing a crafted rich‑data type via a PUT request. The vulnerability arises from improper handling of serialized data, enabling exploitation through code execution. The impact is the ability for an attacker to fully compromise the Puppet Server process, potentially leading to system compromise, data theft, and denial of service.

Vulnerable to Perforce Puppet Enterprise releases that utilize puppet-agent before version 8.22.2 or 9.1.3. The affected releases include Puppet Enterprise 2023.8.13, 2025.12.1, and 2026.0.1. Updating to these releases or newer ensures the fixed code is loaded and mitigates the risk.

The CVSS score of 9.4 indicates critical severity. EPSS is not available, so the exploitation probability is uncertain, but the vulnerability is not currently listed in CISA KEV. Based on the description, the likely attack vector requires a client with a CA‑signed agent certificate; if the certificate authority autosigns requests without strong verification, an unauthenticated network attacker could obtain such a certificate, expanding the exploitability window.