CVE-2026-100689

GitPython before 3.1.62 does not validate the path field read from an untrusted .gitmodules file when updating submodules. While a prior fix (GHSA-hmq2-w58f-27jc) added Submodule._validated_name() to constrain the name field, and GitPython's own containment guard Submodule._to_relative_path() is applied in add() and move(), Submodule.update() derives the absolute checkout location from the raw path value without that guard. A .gitmodules entry containing directory traversal components (e.g., path = ../../../tmp/escaped) can therefore cause directories to be created via os.makedirs() outside the repository working tree, populated from the submodule URL on the clone path, and removed via shutil.rmtree() when force_remove is used. Exploitation requires an application flow that updates submodules at a non-HEAD commit (such as a historical-commit API); the common clone-then-update flow re-derives the path from a canonical tree lookup and is not affected. The issue is fixed in GitPython 3.1.62.

GitPython before 3.1.62 does not validate the path field read from an untrusted .gitmodules file when updating submodules. While a prior fix (GHSA-hmq2-w58f-27jc) added Submodule._validated_name() to constrain the name field, and GitPython's own containment guard Submodule._to_relative_path() is applied in add() and move(), Submodule.update() derives the absolute checkout location from the raw path value without that guard. A .gitmodules entry containing directory traversal components (e.g., path = ../../../tmp/escaped) can therefore cause directories to be created via os.makedirs() outside the repository working tree, populated from the submodule URL on the clone path, and removed via shutil.rmtree() when force_remove is used. Exploitation requires an application flow that updates submodules at a non-HEAD commit (such as a historical-commit API); the common clone-then-update flow re-derives the path from a canonical tree lookup and is not affected. The issue is fixed in GitPython 3.1.62.

Affected: GitPython 3.1.61 (latest release) and main — git/objects/submodule/base.py. git diff 3.1.61 origin/main -- git/objects/submodule/ is empty, so both are identical here.

The gap

The fix for GHSA-hmq2-w58f-27jc added Submodule._validated_name() and wired it into update() and five siblings, closing the .gitmodules name → .git/modules/<name> traversal. The other attacker-controlled .gitmodules field, path, is read raw:

# git/objects/submodule/base.py:172-177
def _set_cache_(self, attr):
    if attr in ("path", "_url", "_branch_path"):
        reader = self.config_reader()
        self.path = reader.get("path")          # raw .gitmodules value

and GitPython's own containment guard is applied in only two of the places that consume it:

400: def _to_relative_path(cls, parent_repo, path)      # the guard (abspath + commonpath containment)
542:     path = cls._to_relative_path(repo, path)        # add()   — guarded
1041:    module_checkout_path = self._to_relative_path(self.repo, module_path)   # move() — guarded

update() validates only the name and then uses the path-derived absolute location directly:

788:  self._validated_name(self.name)                    # NAME only
801:  checkout_module_abspath = self.abspath             # derived from self.path — unguarded
821:  os.makedirs(checkout_module_abspath, exist_ok=True)

So path = ../../../tmp/escaped in an attacker-authored .gitmodules selects the directory that gets created and, on the clone path, populated from the submodule URL. The same absolute location is what force_remove hands to shutil.rmtree.

The asymmetry is the argument: this is not a missing concept — the project wrote _to_relative_path() precisely for this, and add()/move() use it. update() does not.

Honest limits (please read before rating)

• The most common flow is not affected. Repo.clone_from(...) → repo.submodules → sm.update(init=True) re-derives path from a canonical tree lookup, and real git refuses to check out a tree containing a .. component, so an evil .gitmodules never lands in the working tree in the first place. A reachable trigger therefore requires the victim's code to name a non-HEAD commit (a historical-commit API such as submodule_update(previous_commit=...)).
• The researcher did not build that end-to-end trigger. The researcher only verified first-hand the code above: the guard's two call sites, the name-only validation in update(), and the unguarded abspath → os.makedirs() flow at 3.1.61 == main.

Suggested fix

Apply the guard the project already has, wherever the path is consumed:

# in update(), before deriving abspath (and in any other consumer of self.path):
checkout_rel = self._to_relative_path(self.repo, self.path)   # raises if it escapes the working tree

Better still, validate at the boundary: reject a .gitmodules entry whose path is absolute or contains a .. component when the section is first read in _set_cache_()/iter_items(), so no consumer can be added later without the check. A regression test with path = ../escaped alongside the existing name test would pin both fields.

Prior art checked

GHSA-hmq2-w58f-27jc (this is a residual of its fix, in the sibling field, not a re-report) plus the repository's 30 published advisories — none mentions the path field or _to_relative_path. Searched issues and PRs for _to_relative_path, gitmodules path and submodule traversal: no report of this.

Credit

kta1kri.

Appendix — EVIDENCE_gitpython_path_unguarded_20260901.txt (inlined; advisories accept no attachments)

=== EVIDENCE: GitPython — the .gitmodules 'path' field reaches os.makedirs()/clone unguarded ===
Mon Aug 31 18:45:22 UTC 2026

--- artifact: tag 3.1.61 (latest release); git diff 3.1.61 origin/main -- git/objects/submodule/ is empty ---

---…

GitPython before 3.1.62 does not validate the path field read from an untrusted .gitmodules file when updating submodules. While a prior fix (GHSA-hmq2-w58f-27jc) added Submodule._validated_name() to constrain the name field, and GitPython's own containment guard Submodule._to_relative_path() is applied in add() and move(), Submodule.update() derives the absolute checkout location from the raw path value without that guard. A .gitmodules entry containing directory traversal components (e.g., path = ../../../tmp/escaped) can therefore cause directories to be created via os.makedirs() outside the repository working tree, populated from the submodule URL on the clone path, and removed via shutil.rmtree() when force_remove is used. Exploitation requires an application flow that updates submodules at a non-HEAD commit (such as a historical-commit API); the common clone-then-update flow re-derives the path from a canonical tree lookup and is not affected. The issue is fixed in GitPython 3.1.62.

GitPython before 3.1.62 does not validate the path field read from an untrusted .gitmodules file when updating submodules. While a prior fix (GHSA-hmq2-w58f-27jc) added Submodule._validated_name() to constrain the name field, and GitPython's own containment guard Submodule._to_relative_path() is applied in add() and move(), Submodule.update() derives the absolute checkout location from the raw path value without that guard. A .gitmodules entry containing directory traversal components (e.g., path = ../../../tmp/escaped) can therefore cause directories to be created via os.makedirs() outside the repository working tree, populated from the submodule URL on the clone path, and removed via shutil.rmtree() when force_remove is used. Exploitation requires an application flow that updates submodules at a non-HEAD commit (such as a historical-commit API); the common clone-then-update flow re-derives the path from a canonical tree lookup and is not affected. The issue is fixed in GitPython 3.1.62.

GitPython before 3.1.62 does not validate the path field read from an untrusted .gitmodules file when updating submodules. While a prior fix (GHSA-hmq2-w58f-27jc) added Submodule._validated_name() to constrain the name field, and GitPython's own containment guard Submodule._to_relative_path() is applied in add() and move(), Submodule.update() derives the absolute checkout location from the raw path value without that guard. A .gitmodules entry containing directory traversal components (e.g., path = ../../../tmp/escaped) can therefore cause directories to be created via os.makedirs() outside the repository working tree, populated from the submodule URL on the clone path, and removed via shutil.rmtree() when force_remove is used. Exploitation requires an application flow that updates submodules at a non-HEAD commit (such as a historical-commit API); the common clone-then-update flow re-derives the path from a canonical tree lookup and is not affected. The issue is fixed in GitPython 3.1.62.