{"id":"PYSEC-2026-2890","summary":"Poetry has Path Traversal in tar extraction on Python 3.10.0 - 3.10.12 and 3.11.0 - 3.11.4","details":"### Summary\n\nThe `extractall()` function in `src/poetry/utils/helpers.py:410-426` extracts sdist tarballs without path traversal protection on Python versions where `tarfile.data_filter` is unavailable. Considering only Python versions which are still supported by Poetry, these are 3.10.0 - 3.10.12 and 3.11.0 - 3.11.4.\n\n### Impact\n\nArbitrary file write (path traversal) from untrusted sdist content.\n\n**In practice, the impact is low** because an attacker who exploits this vulnerability can as well include arbitrary code in a `setup.py`, which will be executed when the sdist is built after tar extraction. In other words, a malicious sdist can write arbitrary files by design. However, since it is unexpected and not by design that the file write already happens during tar extraction, this is still considered a vulnerability.\n\nOn Python 3.11.2 (Debian Bookworm default, directly tested), a crafted sdist with `../../` tar member paths writes files outside the intended extraction directory. The traversal occurs during metadata resolution (`poetry add --lock`), before the build backend is run.\n\nAffected Environments: \n- **Python 3.10.0 through 3.10.12** (inclusive): `tarfile.data_filter` absent or broken\n- **Python 3.11.0 through 3.11.4** (inclusive): `tarfile.data_filter` absent or broken\n- **Debian Bookworm**: Python 3.11.2 (default)\n- **Ubuntu 22.04 LTS**: Python 3.10.6 (default)\n\n### Patches\n\nVersions 2.3.4 and newer of Poetry ensure that paths are inside the target directory.\n\n### Root Cause\n\nFile: `src/poetry/utils/helpers.py`, lines 410-426:\n\n```python\ndef extractall(source: Path, dest: Path, zip: bool) -\u003e None:\n    \"\"\"Extract all members from either a zip or tar archive.\"\"\"\n    if zip:\n        with zipfile.ZipFile(source) as archive:\n            archive.extractall(dest)\n    else:\n        broken_tarfile_filter = {(3, 9, 17), (3, 10, 12), (3, 11, 4)}\n        with tarfile.open(source) as archive:\n            if (\n                hasattr(tarfile, \"data_filter\")\n                and sys.version_info[:3] not in broken_tarfile_filter\n            ):\n                archive.extractall(dest, filter=\"data\")\n            else:\n                archive.extractall(dest)  # \u003c-- NO FILTER: path traversal\n```\n\nOn Python versions without a working `tarfile.data_filter`, the `else` branch at line 426 calls `tarfile.extractall()` without any filter or path validation. This enables three attack vectors:\n\n1. **Direct path traversal**: Tar members with `../../` path components write files outside the extraction directory.\n2. **Symlink traversal**: A symlink member pointing outside dest, followed by a file written through that symlink, escapes the boundary.\n3. **Hardlink attacks**: Hardlink members can read arbitrary files (same inode) or overwrite targets outside dest.\n\n#### Call Sites\n\nThis function is called from two locations:\n\n1. **`src/poetry/installation/chef.py:104`** (`_prepare_sdist`): During `poetry install` / `poetry add` when building a package from sdist. Only triggered when the executor is enabled (actual installation).\n\n2. **`src/poetry/inspection/info.py:322`** (`_from_sdist_file`): During dependency resolution (`poetry lock` / `poetry add`). This path is reached when the sdist's `PKG-INFO` lacks `Requires-Dist` metadata, forcing Poetry to extract the archive (and afterwards build the package).\n\n### Suggested Fix\n\nApply path validation in the `else` branch, covering direct traversal, symlinks, and hardlinks:\n\n```python\ndef extractall(source: Path, dest: Path, zip: bool) -\u003e None:\n    \"\"\"Extract all members from either a zip or tar archive.\"\"\"\n    if zip:\n        with zipfile.ZipFile(source) as archive:\n            archive.extractall(dest)\n    else:\n        broken_tarfile_filter = {(3, 9, 17), (3, 10, 12), (3, 11, 4)}\n        with tarfile.open(source) as archive:\n            if (\n                hasattr(tarfile, \"data_filter\")\n                and sys.version_info[:3] not in broken_tarfile_filter\n            ):\n                archive.extractall(dest, filter=\"data\")\n            else:\n                # Validate all member paths before extraction\n                dest_resolved = dest.resolve()\n                safe_members = []\n                for member in archive.getmembers():\n                    member_path = (dest_resolved / member.name).resolve()\n                    if not member_path.is_relative_to(dest_resolved):\n                        raise ValueError(\n                            f\"Refusing to extract {member.name}: \"\n                            f\"would write outside {dest}\"\n                        )\n                    if member.issym():\n                        link_target = (member_path.parent / member.linkname).resolve()\n                        if not link_target.is_relative_to(dest_resolved):\n                            raise ValueError(\n                                f\"Refusing symlink {member.name}: \"\n                                f\"target {member.linkname} outside {dest}\"\n                            )\n                    elif member.islnk():\n                        link_target = (dest_resolved / member.linkname).resolve()\n                        if not link_target.is_relative_to(dest_resolved):\n                            raise ValueError(\n                                f\"Refusing hardlink {member.name}: \"\n                                f\"target {member.linkname} outside {dest}\"\n                            )\n                    safe_members.append(member)\n                archive.extractall(dest, members=safe_members)\n```","aliases":["CVE-2026-41140","GHSA-73h3-mf4w-8647"],"modified":"2026-07-13T16:32:58.805584132Z","published":"2026-07-13T15:02:52.466566Z","references":[{"type":"WEB","url":"https://github.com/python-poetry/poetry/security/advisories/GHSA-73h3-mf4w-8647"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-41140"},{"type":"PACKAGE","url":"https://github.com/python-poetry/poetry"},{"type":"WEB","url":"https://github.com/python-poetry/poetry/releases/tag/2.3.4"},{"type":"PACKAGE","url":"https://pypi.org/project/poetry"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-73h3-mf4w-8647"}],"affected":[{"package":{"name":"poetry","ecosystem":"PyPI","purl":"pkg:pypi/poetry"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.3.4"}]}],"versions":["0.1.0","0.10.0","0.10.0a0","0.10.0a1","0.10.0a2","0.10.0a3","0.10.1","0.10.2","0.10.3","0.11.0","0.11.0a0","0.11.0a1","0.11.0a2","0.11.0a3","0.11.0a4","0.11.1","0.11.2","0.11.3","0.11.4","0.11.5","0.12.0","0.12.0a0","0.12.0a1","0.12.0a2","0.12.0a3","0.12.0a4","0.12.0a5","0.12.1","0.12.10","0.12.11","0.12.12","0.12.13","0.12.14","0.12.15","0.12.16","0.12.17","0.12.2","0.12.3","0.12.4","0.12.5","0.12.6","0.12.7","0.12.8","0.12.9","0.2.0","0.3.0","0.4.0","0.4.0.post1","0.4.1","0.4.2","0.5.0","0.5.0b1","0.5.0b2","0.6.0","0.6.1","0.6.2","0.6.3","0.6.3b1","0.6.3b2","0.6.3b3","0.6.3b4","0.6.3b5","0.6.3b6","0.6.3b7","0.6.4","0.6.4b1","0.6.5","0.7.0","0.7.0b1","0.7.0b2","0.7.0b3","0.7.0b4","0.7.1","0.8.0","0.8.0a0","0.8.0a1","0.8.0a2","0.8.0a3","0.8.0a4","0.8.1","0.8.1a0","0.8.2","0.8.3","0.8.4","0.8.5","0.8.5a0","0.8.6","0.9.0","0.9.0a0","0.9.0a1","0.9.0a2","0.9.0a3","0.9.1","1.0.0","1.0.0a0","1.0.0a1","1.0.0a2","1.0.0a3","1.0.0a4","1.0.0a5","1.0.0b1","1.0.0b2","1.0.0b3","1.0.0b4","1.0.0b5","1.0.0b6","1.0.0b7","1.0.0b8","1.0.0b9","1.0.1","1.0.10","1.0.2","1.0.3","1.0.4","1.0.5","1.0.6","1.0.7","1.0.8","1.0.9","1.1.0","1.1.0a1","1.1.0a2","1.1.0a3","1.1.0b1","1.1.0b2","1.1.0b3","1.1.0b4","1.1.0rc1","1.1.1","1.1.10","1.1.11","1.1.12","1.1.13","1.1.14","1.1.15","1.1.2","1.1.3","1.1.4","1.1.5","1.1.6","1.1.7","1.1.8","1.1.9","1.2.0","1.2.0a1","1.2.0a2","1.2.0b1","1.2.0b2","1.2.0b3","1.2.0rc1","1.2.0rc2","1.2.1","1.2.2","1.3.0","1.3.1","1.3.2","1.4.0","1.4.1","1.4.2","1.5.0","1.5.1","1.6.0","1.6.1","1.7.0","1.7.1","1.8.0","1.8.1","1.8.2","1.8.3","1.8.4","1.8.5","2.0.0","2.0.1","2.1.0","2.1.1","2.1.2","2.1.3","2.1.4","2.2.0","2.2.1","2.3.0","2.3.1","2.3.2","2.3.3"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/poetry/PYSEC-2026-2890.yaml"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U"}]}