Low

Poetry has Path Traversal in tar extraction on Python 3.10.0 - 3.10.12 and 3.11.0 - 3.11.4

  • Disclosed: 22.04.2026
  • Updated: 11.10.2026 14:17

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_filter absent or broken
  • Python 3.11.0 through 3.11.4 (inclusive): tarfile.data_filter absent 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:

python
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:

  1. Direct path traversal: Tar members with ../../ path components write files outside the extraction directory.
  2. Symlink traversal: A symlink member pointing outside dest, followed by a file written through that symlink, escapes the boundary.
  3. Hardlink attacks: Hardlink members can read arbitrary files (same inode) or overwrite targets outside dest.

Call Sites

This function is called from two locations:

  1. 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).

  2. 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).

Suggested Fix

Apply path validation in the else branch, covering direct traversal, symlinks, and hardlinks:

python
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.

PlatformPackageVulnerable versionsFixed in
Python (PyPI) poetry < 2.3.4 2.3.4

References

CVSS score -
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

  1. 2022: 3
  2. 2023: 0
  3. 2024: 0
  4. 2025: 0
  5. 2026: 2
  1. Poetry has Path Traversal in tar extraction on Python 3.10.0 - 3.10.12 and 3.11.0 - 3.11.4 this entry
    Low CVE-2026-41140 < 2.3.4 2.3.4
  2. High · 6.5 CVE-2026-34591 >= 1.4.0, < 2.3.3 2.3.3
  3. High · 7.3 CVE-2022-36069 < 1.1.9 1.1.9
  4. Critical · 9.8 CVE-2022-26184 < 1.1.9 1.1.9

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