{"id":"CVE-2026-44513","aliases":["GHSA-98h9-4798-4q5v","PYSEC-2026-40"],"url":"https://o3.security/vulnerability/CVE-2026-44513","summary":"Diffusers: `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","published":"2026-05-14T16:26:03.907Z","modified":"2026-08-30T03:30:48.380499896Z","cvss":{"score":8.8,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"},"epss":{"score":0.00848,"percentile":0.55025,"asOf":"2026-08-15"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"diffusers","fixedVersion":"0.38.0"}],"fix":{"url":"https://github.com/huggingface/diffusers/pull/13448","label":"huggingface/diffusers#13448"},"references":[{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44513.json"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:60520"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-44513"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44513.json"},{"type":"ADVISORY","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":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2477507"},{"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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-30T03:30:48.380499896Z"}}