CVE-2026-44513: Diffusers Diffusers Has A `trust_remote_code` Bypass Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-98h9-4798-4q5v",
  "modified" : "2026-06-05T17:53:10Z",
  "published" : "2026-05-07T05:31:17Z",
  "aliases" : [ "CVE-2026-44513" ],
  "summary" : "Diffusers has a `trust_remote_code` bypass via `custom_pipeline` and local custom components",
  "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 — 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('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.\n2. **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.\n3. **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.\n\nSilent remote code execution on the victim's 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 `< 0.38.0` should upgrade:\n\n```bash\npip install --upgrade \"diffusers>=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 — 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",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "diffusers"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.38.0"
      } ]
    } ]
  } ],
  "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"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/diffusers/PYSEC-2026-40.yaml"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-94" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-07T05:31:17Z",
    "nvd_published_at" : "2026-05-14T17:16:22Z"
  }
}