Transformers save_pretrained path traversal allows arbitrary file writes through chat template names
A vulnerability in huggingface/transformers versions < 5.10.0 allows an attacker to perform arbitrary file writes via path traversal. The issue resides in the save_pretrained() methods of PreTrainedTokenizerBase and ProcessorMixin, where keys from the chat_template dictionary are used directly as filenames without proper validation. An attacker can exploit this by publishing a malicious Hugging Face Hub repository with a crafted tokenizer_config.json file. When a victim downloads and saves the tokenizer or processor, the attacker-controlled keys can escape the intended save directory, enabling arbitrary file writes with attacker-controlled content. This vulnerability affects multiple processors inheriting from ProcessorMixin, including Idefics, Florence, Gemma, Phi, and Qwen-VL.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | transformers | < 5.10.0 | 5.10.0 |
References
- https://nvd.nist.gov/vuln/detail/CVE-2026-9856
- https://github.com/huggingface/transformers/pull/46191
- https://github.com/huggingface/transformers/commit/eaaaf8494dd5386634ae37d1d122212fdc315be5
- https://github.com/huggingface/transformers
- https://huntr.com/bounties/362824d5-fe18-40e8-a6cf-62277f97a170
- https://pypi.org/project/transformers
- https://github.com/advisories/GHSA-xrqw-3rrv-vx5w
- CVSS vector
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L- Weakness (CWE)
CWE-22- Platform
- Python (PyPI)
- Package
transformers- Disclosed
- 02.08.2026
- Updated
- 11.10.2026 15:18
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-3929 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-xrqw-3rrv-vx5w - CC BY 4.0
Vulnerability history: transformers
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 32
- First → latest
- 05.2023 09.2026
- Without a fix
- 9
- Exploited in attacks
- 0
Severity breakdown
- High 18
- Medium 12
- Low 2
Disclosures per year
- 2023: 3
- 2024: 4
- 2025: 20
- 2026: 5
-
Transformers save_pretrained path traversal allows arbitrary file writes through chat template names this entry
Know which vulnerabilities affect your application
With the DockRay integration and software inventory enabled, DockRay checks reported component versions against known vulnerabilities and notifies you about confirmed matches. Coverage depends on the supported technology and available advisory data.