Poetry has Path Traversal in tar extraction on Python 3.10.0 - 3.10.12 and 3.11.0 - 3.11.4
Summary
The 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.
Impact
Arbitrary file write (path traversal) from untrusted sdist content.
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.
On 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.
Affected Environments:
- Python 3.10.0 through 3.10.12 (inclusive):
tarfile.data_filterabsent or broken - Python 3.11.0 through 3.11.4 (inclusive):
tarfile.data_filterabsent or broken - Debian Bookworm: Python 3.11.2 (default)
- Ubuntu 22.04 LTS: Python 3.10.6 (default)
Patches
Versions 2.3.4 and newer of Poetry ensure that paths are inside the target directory.
Root Cause
File: src/poetry/utils/helpers.py, lines 410-426:
def extractall(source: Path, dest: Path, zip: bool) -> None:
"""Extract all members from either a zip or tar archive."""
if zip:
with zipfile.ZipFile(source) as archive:
archive.extractall(dest)
else:
broken_tarfile_filter = {(3, 9, 17), (3, 10, 12), (3, 11, 4)}
with tarfile.open(source) as archive:
if (
hasattr(tarfile, "data_filter")
and sys.version_info[:3] not in broken_tarfile_filter
):
archive.extractall(dest, filter="data")
else:
archive.extractall(dest) # <-- NO FILTER: path traversal
On 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:
- Direct path traversal: Tar members with
../../path components write files outside the extraction directory. - Symlink traversal: A symlink member pointing outside dest, followed by a file written through that symlink, escapes the boundary.
- Hardlink attacks: Hardlink members can read arbitrary files (same inode) or overwrite targets outside dest.
Call Sites
This function is called from two locations:
-
src/poetry/installation/chef.py:104(_prepare_sdist): Duringpoetry install/poetry addwhen building a package from sdist. Only triggered when the executor is enabled (actual installation). -
src/poetry/inspection/info.py:322(_from_sdist_file): During dependency resolution (poetry lock/poetry add). This path is reached when the sdist'sPKG-INFOlacksRequires-Distmetadata, forcing Poetry to extract the archive (and afterwards build the package).
Suggested Fix
Apply path validation in the else branch, covering direct traversal, symlinks, and hardlinks:
def extractall(source: Path, dest: Path, zip: bool) -> None:
"""Extract all members from either a zip or tar archive."""
if zip:
with zipfile.ZipFile(source) as archive:
archive.extractall(dest)
else:
broken_tarfile_filter = {(3, 9, 17), (3, 10, 12), (3, 11, 4)}
with tarfile.open(source) as archive:
if (
hasattr(tarfile, "data_filter")
and sys.version_info[:3] not in broken_tarfile_filter
):
archive.extractall(dest, filter="data")
else:
# Validate all member paths before extraction
dest_resolved = dest.resolve()
safe_members = []
for member in archive.getmembers():
member_path = (dest_resolved / member.name).resolve()
if not member_path.is_relative_to(dest_resolved):
raise ValueError(
f"Refusing to extract {member.name}: "
f"would write outside {dest}"
)
if member.issym():
link_target = (member_path.parent / member.linkname).resolve()
if not link_target.is_relative_to(dest_resolved):
raise ValueError(
f"Refusing symlink {member.name}: "
f"target {member.linkname} outside {dest}"
)
elif member.islnk():
link_target = (dest_resolved / member.linkname).resolve()
if not link_target.is_relative_to(dest_resolved):
raise ValueError(
f"Refusing hardlink {member.name}: "
f"target {member.linkname} outside {dest}"
)
safe_members.append(member)
archive.extractall(dest, members=safe_members)
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | poetry | < 2.3.4 | 2.3.4 |
References
- https://github.com/python-poetry/poetry/security/advisories/GHSA-73h3-mf4w-8647
- https://nvd.nist.gov/vuln/detail/CVE-2026-41140
- https://github.com/python-poetry/poetry
- https://github.com/python-poetry/poetry/releases/tag/2.3.4
- https://pypi.org/project/poetry
- https://github.com/advisories/GHSA-73h3-mf4w-8647
- CVSS vector
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- Weakness (CWE)
CWE-22- Platform
- Python (PyPI)
- Package
poetry- Disclosed
- 22.04.2026
- Updated
- 11.10.2026 14:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-2890 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-73h3-mf4w-8647 - CC BY 4.0
Vulnerability history: poetry
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 5
- First → latest
- 03.2022 04.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- High 3
- Low 1
Disclosures per year
- 2022: 3
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 2
-
Poetry has Path Traversal in tar extraction on Python 3.10.0 - 3.10.12 and 3.11.0 - 3.11.4 this entry
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