PyPI · Gitpython
GitPython validates a submodule's ".git" path only after cloning into it (RCE)
create_submodule(name, path, url) clones a submodule into the repo's own .git
directory before it rejects the path. A path of ".git/hooks" is accepted by the
pre-clone check, so the submodule is cloned straight into the live hooks directory,
and a file named post-checkout in the submodule becomes an executable
.git/hooks/post-checkout. On 3.2.0+ the later index check does raise ValueError,
but only after the clone already wrote to disk, and it does not remove the planted
hook; on 3.1.x there is no such check and the call succeeds silently. Either way the
hook runs on the next git operation (e.g. checkout), giving code execution.
The checkout path is validated too late, after the clone has already mutated disk. This breaks the "validate before mutation" invariant that commit 43a43cd8 ("Validate submodule checkout and metadata paths before mutation") set out to enforce.
Submodule.add() calls the permissive path check before cloning, and the strict check only reaches the ".git" alias at index time, after _clone_repo has written to disk:
git/objects/submodule/base.py (Submodule.add)
599: path = cls._to_relative_path(repo, path) # accepts ".git/hooks"
673: mrepo = cls._clone_repo(repo, url, path, name, ...) # clones into
git/index/base.py (IndexFile._preprocess_add_items) 732: _validate_repo_path(entry.path) # rejects ".git", too late
_to_relative_path only blocks ../absolute/out-of-tree paths; .git aliases are
rejected only by _validate_repo_path, which was added in 3.2.0 (commit a75aedf3) and
runs at the index boundary. The ValueError it raises at line 732 does not roll back
what _clone_repo already wrote.
Version-dependent behavior:
.git; create_submodule(path=".git/hooks", ...) returns with no error at
all and the hook is planted silently.Setup:
evilsub/ : a git repo whose ROOT contains an executable file named post-checkout (the payload)
victim/ : a git repo with at least 1 commit and a second branch, whose .git/hooks has NO
sample hooks (the state of a minimal/CI checkout, or git init with an empty
template dir, or GIT_TEMPLATE_DIR/init.templateDir empty)
import git, os.path as osp try: git.Repo("victim").create_submodule(name="x", path=".git/hooks", url=osp.abspath("evilsub")) except ValueError: pass # 3.2.0+: ".git" is rejected, but only AFTER the clone, so the plant already happened. # 3.1.x: no exception is raised at all; the call succeeds and still plants the hook.
Verified live:
git checkout executed it.git checkout.Arbitrary code execution. A library/app that creates a submodule from an
attacker-influenced path ends up with an attacker-controlled executable in
.git/hooks, which git runs on ordinary later operations. This affects any service
that derives a submodule checkout path from untrusted data, e.g. one that ingests a
submodule spec (name/path/url) from a user-supplied manifest or API request and feeds
path into create_submodule. On 3.2.0+ the library's own validation is the thing that
fails: it correctly rejects the .git path, but only after the submodule has already
been cloned into place, so an app that traps the ValueError reasonably believes the
unsafe path was blocked.
Preconditions (hence AC:H): (1) the app passes an attacker-influenced submodule path;
(2) the target hook name is free in .git/hooks, true for minimal/CI/container
checkouts and whenever init.templateDir/GIT_TEMPLATE_DIR is empty. With the default
sample hooks present, git clone refuses the non-empty destination and no plant occurs.
Affected: all tested versions from 3.1.x (3.1.59) through the current tip bda18e08 (3.2.0 + 3 commits). 3.1.x plants silently; 3.2.0+ plants despite raising ValueError.
Is your project exposed to this? Stateward checks every dependency on every pull request and flags it only if your code actually reaches it.
Check my repoSources: CISA KEV (public domain), OSV.dev & GitHub Advisory Database (CC-BY-4.0), FIRST EPSS, NVD/CWE (public domain). Served live from the Stateward advisory database.