GitPython CVE-2026-67324: One-character shorthand bypasses remote code execution guard

A critical vulnerability in GitPython, tracked as CVE-2026-67324 and scored 9.8 on CVSS 3.1, allows attackers to bypass the library's built-in guard against dangerous git options. The flaw affects version 3.1.50, where the security check blocks the long-form flag --upload-pack but fails to catch its short-form equivalent -u, enabling arbitrary command execution even when allow_unsafe_options is set to False. Exploitation requires that user-influenced input reaches the multi_options parameter of Repo.clone_from, a scenario common in CI pipelines, web forms, and tools that accept repository URLs or build parameters. GitPython is downloaded roughly 254 million times monthly on PyPI, arriving as a dependency of widely used tools such as MLflow, DVC, and Semgrep, significantly broadening the attack surface. Version 3.1.51 patches the issue, and this is reportedly the third bypass of the same security barrier within a single year, all sharing the same root cause.