AIKIDO-2026-451908

TL;DR

build_index_from_tree in dulwich/index.py materializes checkout and index entries without verifying that the leading path components of each entry resolve inside the work tree. A crafted tree that contains a symlink entry (for example link pointing to an absolute or out-of-tree target) followed by an entry beneath it (link/foo) causes files to be written through the symlink to an arbitrary filesystem location. Checking out or cloning a malicious repository can therefore overwrite sensitive files such as .git/hooks, which leads to remote code execution on a later git operation. The fix applies the verify_leading_dirs guard so entries whose leading path resolves through a symlink are refused.