GHSA-98H9-4798-4Q5V

Vulnerability from github – Published: 2026-05-07 05:31 – Updated: 2026-05-14 20:53
VLAI?
Summary
Diffusers has a `trust_remote_code` bypass via `custom_pipeline` and local custom components
Details

Impact

A trust_remote_code bypass in DiffusionPipeline.from_pretrained allows arbitrary remote code execution despite the user passing trust_remote_code=False (or omitting it, which is the default). The vulnerability has three variants, all sharing the same root cause — the trust_remote_code gate was implemented inside DiffusionPipeline.download() rather than at the actual dynamic-module load site, so any code path that bypassed or short-circuited download() also bypassed the security check:

  1. Cross-repo custom_pipeline. DiffusionPipeline.from_pretrained('repoA', custom_pipeline='attacker/repoB', trust_remote_code=False) — the gate evaluated against repoA's file list rather than repoB's, so repoB's pipeline.py was loaded and executed.
  2. Local snapshot + Hub custom_pipeline. DiffusionPipeline.from_pretrained('/local/snapshot', custom_pipeline='attacker/repoB', trust_remote_code=False) — the local-path branch never invoked download(), so the gate was never reached and remote code from repoB executed.
  3. Local snapshot with custom components. DiffusionPipeline.from_pretrained('/local/snapshot', trust_remote_code=False) where the snapshot contains custom component files (e.g. unet/my_unet_model.py) referenced from model_index.json — same root cause; the local path skipped download() and custom component code executed.

Silent remote code execution on the victim's machine. Anyone calling DiffusionPipeline.from_pretrained with custom pipelines is impacted.

Patches

Yes. Fixed in diffusers 0.38.0 via PR #13448. All users on versions < 0.38.0 should upgrade:

pip install --upgrade "diffusers>=0.38.0"

The fix moves the trust_remote_code gate out of DiffusionPipeline.download() and into get_cached_module_file in src/diffusers/utils/dynamic_modules_utils.py, which is the actual chokepoint for every dynamic module load (local, Hub, or community mirror). All three variants now raise ValueError instead of executing untrusted code.

Workarounds

If upgrading immediately is not possible:

  • Only call from_pretrained with pretrained_model_name_or_path, custom_pipeline, and local snapshot directories from fully trusted sources that have been audited.
  • Do not pass custom_pipeline= pointing at a Hub repository different from the primary pretrained_model_name_or_path before reading its pipeline.py.
  • Before calling from_pretrained on a local snapshot, inspect the snapshot for unexpected *.py files, especially under component subdirectories (unet/, scheduler/, etc.) and at the snapshot root.

These are mitigations, not fixes — the only complete remediation is upgrading to 0.38.0.

Resources

  • Fix: https://github.com/huggingface/diffusers/pull/13448
  • Original issue: https://github.com/huggingface/diffusers/issues/13446
  • Release notes: https://github.com/huggingface/diffusers/releases/tag/v0.38.0
  • CWE-94: https://cwe.mitre.org/data/definitions/94.html
Severity ?
8.8 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Show details on source website
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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "diffusers"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.38.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-44513"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-94"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-07T05:31:17Z",
    "nvd_published_at": "2026-05-14T17:16:22Z",
    "severity": "HIGH"
  },
  "details": "### Impact\n\nA `trust_remote_code` bypass in `DiffusionPipeline.from_pretrained` allows arbitrary remote code execution despite the user passing `trust_remote_code=False` (or omitting it, which is the default). The vulnerability has three variants, all sharing the same root cause \u2014 the `trust_remote_code` gate was implemented inside `DiffusionPipeline.download()` rather than at the actual dynamic-module load site, so any code path that bypassed or short-circuited `download()` also bypassed the security check:\n\n1. **Cross-repo `custom_pipeline`.** `DiffusionPipeline.from_pretrained(\u0027repoA\u0027, custom_pipeline=\u0027attacker/repoB\u0027, trust_remote_code=False)` \u2014 the gate evaluated against `repoA`\u0027s file list rather than `repoB`\u0027s, so `repoB`\u0027s `pipeline.py` was loaded and executed.\n2. **Local snapshot + Hub `custom_pipeline`.** `DiffusionPipeline.from_pretrained(\u0027/local/snapshot\u0027, custom_pipeline=\u0027attacker/repoB\u0027, trust_remote_code=False)` \u2014 the local-path branch never invoked `download()`, so the gate was never reached and remote code from `repoB` executed.\n3. **Local snapshot with custom components.** `DiffusionPipeline.from_pretrained(\u0027/local/snapshot\u0027, trust_remote_code=False)` where the snapshot contains custom component files (e.g. `unet/my_unet_model.py`) referenced from `model_index.json` \u2014 same root cause; the local path skipped `download()` and custom component code executed.\n\nSilent remote code execution on the victim\u0027s machine. Anyone calling `DiffusionPipeline.from_pretrained` with custom pipelines is impacted.\n\n### Patches\n\nYes. Fixed in **diffusers 0.38.0** via [PR #13448](https://github.com/huggingface/diffusers/pull/13448). All users on versions `\u003c 0.38.0` should upgrade:\n\n```bash\npip install --upgrade \"diffusers\u003e=0.38.0\"\n```\n\nThe fix moves the `trust_remote_code` gate out of `DiffusionPipeline.download()` and into `get_cached_module_file` in `src/diffusers/utils/dynamic_modules_utils.py`, which is the actual chokepoint for every dynamic module load (local, Hub, or community mirror). All three variants now raise `ValueError` instead of executing untrusted code.\n\n### Workarounds\n\nIf upgrading immediately is not possible:\n\n- Only call `from_pretrained` with `pretrained_model_name_or_path`, `custom_pipeline`, and local snapshot directories from fully trusted sources that have been audited.\n- Do not pass `custom_pipeline=` pointing at a Hub repository different from the primary `pretrained_model_name_or_path` before reading its `pipeline.py`.\n- Before calling `from_pretrained` on a local snapshot, inspect the snapshot for unexpected `*.py` files, especially under component subdirectories (`unet/`, `scheduler/`, etc.) and at the snapshot root.\n\nThese are mitigations, not fixes \u2014 the only complete remediation is upgrading to 0.38.0.\n\n### Resources\n\n- **Fix:** https://github.com/huggingface/diffusers/pull/13448\n- **Original issue:** https://github.com/huggingface/diffusers/issues/13446\n- **Release notes:** https://github.com/huggingface/diffusers/releases/tag/v0.38.0\n- **CWE-94:** https://cwe.mitre.org/data/definitions/94.html",
  "id": "GHSA-98h9-4798-4q5v",
  "modified": "2026-05-14T20:53:29Z",
  "published": "2026-05-07T05:31:17Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/huggingface/diffusers/security/advisories/GHSA-98h9-4798-4q5v"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44513"
    },
    {
      "type": "WEB",
      "url": "https://github.com/huggingface/diffusers/issues/13446"
    },
    {
      "type": "WEB",
      "url": "https://github.com/huggingface/diffusers/pull/13448"
    },
    {
      "type": "WEB",
      "url": "https://github.com/huggingface/diffusers/commit/a37f6f8394ac2a7ee8360c3abea811efe54512b1"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/huggingface/diffusers"
    },
    {
      "type": "WEB",
      "url": "https://github.com/huggingface/diffusers/releases/tag/v0.38.0"
    }
  ],
  "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"
    }
  ],
  "summary": "Diffusers has a `trust_remote_code` bypass via `custom_pipeline` and local custom components"
}


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