Byron · Aug 25, 2026 · Aug 25, 2026 · Aug 25, 2026
diff --git a/VERSION b/VERSION
@@ -1 +1 @@
-3.1.59
+3.1.60
diff --git a/doc/source/changes.rst b/doc/source/changes.rst
@@ -9,6 +9,7 @@ Security fixes for
 
 * https://github.com/gitpython-developers/GitPython/security/advisories/GHSA-g5vv-9gxw-82hx
 * https://github.com/gitpython-developers/GitPython/security/advisories/GHSA-whh4-5q6c-9v3x
+* https://github.com/gitpython-developers/GitPython/security/advisories/GHSA-239g-whfq-7xj9
 
 If you can, also try and provide feedback on the upcoming v4 branch
 https://github.com/gitpython-developers/GitPython/pull/2177 - patches welcome.

diff --git a/git/repo/base.py b/git/repo/base.py
@@ -45,7 +45,6 @@
 
 from .fun import (
     find_submodule_git_dir,
-    find_worktree_git_dir,
     is_git_dir,
     rev_parse,
     touch,
@@ -234,6 +233,10 @@ def __init__(
     ) -> None:
         R"""Create a new :class:`Repo` instance.
 
+        .. note::
+            Repositories using reftable may be opened, but GitPython's direct reference
+            access does not support reftable.
+
         :param path:
             The path to either the worktree directory or the .git directory itself::
 
@@ -268,7 +271,11 @@ def __init__(
             :class:`Repo`
         """
 
-        epath = path or os.getenv("GIT_DIR")
+        git_dir_env = os.getenv("GIT_DIR")
+        object_dir_env = os.getenv("GIT_OBJECT_DIRECTORY")
+        if object_dir_env is not None:
+            object_dir_env = osp.abspath(object_dir_env)
+        epath = path or git_dir_env
         if not epath:
             epath = os.getcwd()
         epath = os.fspath(epath)
@@ -290,37 +297,48 @@ def __init__(
                 raise NoSuchPathError(epath)
 
         # Walk up the path to find the `.git` dir.
-        curpath = epath
-        git_dir = None
+        curpath = os.fspath(epath) if epath is not None else ""
+        git_dir: Optional[str] = None
+        explicit_git_dir = not path and bool(git_dir_env)
         while curpath:
             # ABOUT osp.NORMPATH
             # It's important to normalize the paths, as submodules will otherwise
             # initialize their repo instances with paths that depend on path-portions
             # that will not exist after being removed. It's just cleaner.
-            if (
-                osp.isfile(osp.join(curpath, "gitdir"))
-                and osp.isfile(osp.join(curpath, "commondir"))
-                and osp.isfile(osp.join(curpath, "HEAD"))
-            ):
-                git_dir = curpath
-
-                if "GIT_WORK_TREE" in os.environ:
-                    self._working_tree_dir = os.getenv("GIT_WORK_TREE")
-                else:
-                    # Linked worktree administrative directories store the path to the
-                    # worktree's .git file in their gitdir file (without "gitdir: " prefix).
-                    with open(osp.join(git_dir, "gitdir")) as fp:
-                        worktree_gitfile = fp.read().strip()
+            if not explicit_git_dir:
+                dotgit = osp.join(curpath, ".git")
+                try:
+                    sm_gitpath = find_submodule_git_dir(dotgit)
+                except OSError:
+                    break
+                if sm_gitpath is not None:
+                    # Worktrees can use relative paths as of Git 2.48, so join to curpath.
+                    git_dir = osp.normpath(osp.join(curpath, os.fspath(sm_gitpath)))
+                    self._working_tree_dir = curpath
+                    break
+
+                # Like Git, do not fall back to a bare repository or parent directory when
+                # a non-directory .git entry exists but is not a valid gitfile.
+                if osp.exists(dotgit) and not osp.isdir(dotgit):
+                    break
 
-                    if not osp.isabs(worktree_gitfile):
-                        worktree_gitfile = osp.normpath(osp.join(git_dir, worktree_gitfile))
+            if is_git_dir(curpath):
+                git_dir = curpath
+                if osp.isfile(osp.join(curpath, "gitdir")) and osp.isfile(osp.join(curpath, "commondir")):
+                    if "GIT_WORK_TREE" in os.environ:
+                        self._working_tree_dir = os.getenv("GIT_WORK_TREE")
+                    else:
+                        # Linked worktree administrative directories store the path to
+                        # the worktree's .git file in gitdir (without a "gitdir: " prefix).
+                        with open(osp.join(git_dir, "gitdir")) as fp:
+                            worktree_gitfile = fp.read().strip()
 
-                    self._working_tree_dir = osp.dirname(worktree_gitfile)
+                        if not osp.isabs(worktree_gitfile):
+                            worktree_gitfile = osp.normpath(osp.join(git_dir, worktree_gitfile))
 
-                break
+                        self._working_tree_dir = osp.dirname(worktree_gitfile)
+                    break
 
-            if is_git_dir(curpath):
-                git_dir = curpath
                 # from man git-config : core.worktree
                 # Set the path to the root of the working tree. If GIT_COMMON_DIR
                 # environment variable is set, core.worktree is ignored and not used for
@@ -340,22 +358,7 @@ def __init__(
                     self._working_tree_dir = os.getenv("GIT_WORK_TREE")
                 break
 
-            dotgit = osp.join(curpath, ".git")
-            sm_gitpath = find_submodule_git_dir(dotgit)
-            if sm_gitpath is not None:
-                git_dir = osp.normpath(sm_gitpath)
-
-            sm_gitpath = find_submodule_git_dir(dotgit)
-            if sm_gitpath is None:
-                sm_gitpath = find_worktree_git_dir(dotgit)
-
-            if sm_gitpath is not None:
-                # worktrees can use relative paths as of Git 2.48, so we join to curpath
-                git_dir = osp.normpath(osp.join(curpath, sm_gitpath))
-                self._working_tree_dir = curpath
-                break
-
-            if not search_parent_directories:
+            if explicit_git_dir or not search_parent_directories:
                 break
             curpath, tail = osp.split(curpath)
             if not tail:
@@ -366,19 +369,23 @@ def __init__(
             raise InvalidGitRepositoryError(epath)
         self.git_dir = git_dir
 
+        common_dir_env = os.getenv("GIT_COMMON_DIR")
+        if common_dir_env is not None:
+            self._common_dir = osp.abspath(common_dir_env)
+        else:
+            try:
+                common_dir = os.fsdecode((Path(self.git_dir) / "commondir").read_bytes()).rstrip("\r\n")
+                self._common_dir = osp.join(self.git_dir, common_dir)
+            except OSError:
+                self._common_dir = ""
+
         self._bare = False
         try:
             self._bare = self.config_reader("repository").getboolean("core", "bare")
         except Exception:
             # Let's not assume the option exists, although it should.
             pass
 
-        try:
-            common_dir = (Path(self.git_dir) / "commondir").read_text().splitlines()[0].strip()
-            self._common_dir = osp.join(self.git_dir, common_dir)
-        except OSError:
-            self._common_dir = ""
-
         # Adjust the working directory in case we are actually bare - we didn't know
         # that in the first place.
         if self._bare:
@@ -387,9 +394,15 @@ def __init__(
 
         self.working_dir: PathLike = self._working_tree_dir or self.common_dir
         self.git = self.GitCommandWrapperType(self.working_dir)
+        if common_dir_env is not None:
+            self.git.update_environment(GIT_DIR=os.fspath(self.git_dir), GIT_COMMON_DIR=os.fspath(self.common_dir))
+        elif git_dir_env is not None:
+            self.git.update_environment(GIT_DIR=os.fspath(self.git_dir))
+        if object_dir_env is not None:
+            self.git.update_environment(GIT_OBJECT_DIRECTORY=object_dir_env)
 
         # Special handling, in special times.
-        rootpath = osp.join(self.common_dir, "objects")
+        rootpath = object_dir_env if object_dir_env is not None else osp.join(self.common_dir, "objects")
         if issubclass(odbt, GitCmdObjectDB):
             self.odb = odbt(rootpath, self.git)
         else:
@@ -990,7 +1003,7 @@ def _get_alternates(self) -> List[str]:
         :return:
             List of strings being pathnames of alternates
         """
-        alternates_path = osp.join(self.common_dir, "objects", "info", "alternates")
+        alternates_path = osp.join(self.odb.root_path(), "info", "alternates")
 
         if osp.exists(alternates_path):
             with open(alternates_path, "rb") as f:
@@ -1011,7 +1024,7 @@ def _set_alternates(self, alts: List[str]) -> None:
             The method does not check for the existence of the paths in `alts`, as the
             caller is responsible.
         """
-        alternates_path = osp.join(self.common_dir, "objects", "info", "alternates")
+        alternates_path = osp.join(self.odb.root_path(), "info", "alternates")
         if not alts:
             if osp.isfile(alternates_path):
                 os.remove(alternates_path)

diff --git a/git/repo/fun.py b/git/repo/fun.py
@@ -60,22 +60,61 @@ def touch(filename: str) -> str:
 def is_git_dir(d: PathLike) -> bool:
     """This is taken from the git setup.c:is_git_directory function.
 
+    .. note::
+        This function recognizes repositories using reftable through their
+        compatibility files, but GitPython's direct reference access does not support
+        reftable.
+
     :raise git.exc.WorkTreeRepositoryUnsupported:
         If it sees a worktree directory. It's quite hacky to do that here, but at least
         clearly indicates that we don't support it. There is the unlikely danger to
         throw if we see directories which just look like a worktree dir, but are none.
     """
     if osp.isdir(d):
-        if (osp.isdir(osp.join(d, "objects")) or "GIT_OBJECT_DIRECTORY" in os.environ) and osp.isdir(
-            osp.join(d, "refs")
-        ):
-            headref = osp.join(d, "HEAD")
-            return osp.isfile(headref) or (osp.islink(headref) and os.readlink(headref).startswith("refs"))
-        elif (
-            osp.isfile(osp.join(d, "gitdir"))
-            and osp.isfile(osp.join(d, "commondir"))
-            and osp.isfile(osp.join(d, "gitfile"))
-        ):
+        headref = osp.join(d, "HEAD")
+        if osp.islink(headref):
+            try:
+                valid_head = os.readlink(headref).startswith("refs/")
+            except OSError:
+                valid_head = False
+        else:
+            try:
+                with open(headref, "rb") as fp:
+                    head = fp.read(256)
+            except OSError:
+                valid_head = False
+            else:
+                valid_head = (head.startswith(b"ref:") and head[4:].lstrip().startswith(b"refs/")) or bool(
+                    re.match(rb"(?:[0-9A-Fa-f]{64}|[0-9A-Fa-f]{40})", head)
+                )
+
+        common_dir = os.getenv("GIT_COMMON_DIR")
+        if common_dir == "":
+            return False
+        if common_dir is None:
+            common_dir_file = Path(d) / "commondir"
+            try:
+                common_dir = os.fsdecode(common_dir_file.read_bytes()).rstrip("\r\n")
+            except FileNotFoundError:
+                if osp.lexists(common_dir_file):
+                    return False
+                common_dir = os.fspath(d)
+            except (OSError, UnicodeError):
+                return False
+            else:
+                if not common_dir:
+                    return False
+                try:
+                    common_dir = osp.realpath(osp.join(d, common_dir))
+                except (OSError, ValueError):
+                    return False
+
+        object_dir = os.getenv("GIT_OBJECT_DIRECTORY")
+        if object_dir is None:
+            object_dir = osp.join(common_dir, "objects")
+        if valid_head and osp.isdir(object_dir) and osp.isdir(osp.join(common_dir, "refs")):
+            return True
+        if osp.isfile(osp.join(d, "gitdir")) and osp.isfile(osp.join(d, "commondir")) and osp.isfile(headref):
             raise WorkTreeRepositoryUnsupported(d)
     return False
 
@@ -84,46 +123,39 @@ def find_worktree_git_dir(dotgit: PathLike) -> Optional[str]:
     """Search for a gitdir for this worktree."""
     try:
         statbuf = os.stat(dotgit)
-    except OSError:
+    except (FileNotFoundError, NotADirectoryError):
         return None
-    if not stat.S_ISREG(statbuf.st_mode):
+    if not stat.S_ISREG(statbuf.st_mode) or statbuf.st_size > (1 << 20):
         return None
 
     try:
-        lines = Path(dotgit).read_text().splitlines()
-        for key, value in [line.strip().split(": ") for line in lines]:
-            if key == "gitdir":
-                return value
-    except ValueError:
-        pass
-    return None
+        with open(dotgit, "rb") as fp:
+            content_bytes = fp.read(statbuf.st_size)
+        if len(content_bytes) != statbuf.st_size:
+            return None
+        content = os.fsdecode(content_bytes).rstrip("\r\n")
+    except (OSError, UnicodeError):
+        return None
+    return content[8:] if len(content) >= 9 and content.startswith("gitdir: ") else None
 
 
 def find_submodule_git_dir(d: PathLike) -> Optional[PathLike]:
     """Search for a submodule repo."""
     if is_git_dir(d):
         return d
 
-    try:
-        with open(d) as fp:
-            content = fp.read().rstrip()
-    except IOError:
-        # It's probably not a file.
-        pass
-    else:
-        if content.startswith("gitdir: "):
-            path = content[8:]
-
-            if Git.is_cygwin():
-                # Cygwin creates submodules prefixed with `/cygdrive/...`.
-                # Cygwin git understands Cygwin paths much better than Windows ones.
-                # Also the Cygwin tests are assuming Cygwin paths.
-                path = cygpath(path)
-            if not osp.isabs(path):
-                path = osp.normpath(osp.join(osp.dirname(d), path))
-            return find_submodule_git_dir(path)
-    # END handle exception
-    return None
+    path = find_worktree_git_dir(d)
+    if path is None:
+        return None
+
+    if Git.is_cygwin():
+        # Cygwin creates submodules prefixed with `/cygdrive/...`.
+        # Cygwin git understands Cygwin paths much better than Windows ones.
+        # Also the Cygwin tests are assuming Cygwin paths.
+        path = cygpath(path)
+    if not osp.isabs(path):
+        path = osp.normpath(osp.join(osp.dirname(d), path))
+    return path if is_git_dir(path) else None
 
 
 def short_to_long(odb: "GitCmdObjectDB", hexsha: str) -> Optional[bytes]: