SumatraPDF, a Windows PDF viewer, suffered from incomplete quote‑only escaping in its SelectionTranslate.cpp component. The bug allows attacker‑controlled text from a selection or paste to be embedded verbatim into Windows command lines that invoke external AI translation backends. Because the command line is not properly escaped, an adversary can inject additional CLI flags such as –model, –working‑directory, –approval, or –sandbox‑bypass. This leads to command‑line injection, enabling arbitrary command execution or privilege escalation through the agentic backend. The weakness is a classic example of CWE‑88: Improper Escaping of Command–Line Parameters.

Any installation of SumatraPDF version 3.6.1 or earlier, regardless of build, is vulnerable. The functions BuildGrokTranslateCmdLineTemp, BuildClaudeTranslateCmdLineTemp, and BuildCodexTranslateCmdLineTemp are the affected entry points. When an agentic CLI backend that accepts the injected parameters is present and executed, the vulnerability manifests. The problem exists on the Windows platform only.

The CVSS score of 7.1 places the flaw in the high‑severity range, indicating a substantial risk to confidentiality, integrity, and availability. The EPSS score is not available, but the lack of a publicly known exploit and the requirement for a specific user action (selecting or copying text) suggest a moderate exploitation probability. The issue is not listed in the CISA KEV catalog, so no active zero‑day evidence is reported. Attackers would need to supply malicious text within the application's interface; once the templated command line is invoked, the injected flags could allow configuration changes or arbitrary code execution depending on the capabilities of the backend.