Vulnerability · Published Aug 2, 2026 · Assigned by @huntr_ai
CVE-2026-9856Path Traversal in huggingface/transformers
High 7.1
In plain English
A high-severity path traversal in huggingface/transformers from huggingface. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 40% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
A vulnerability in huggingface/transformers versions <=5.8.0.dev0 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | transformers | 5.10.0 | GHSA-xrqw-3rrv-vx5w |
| PyPI | transformers | 5.10.0 | PYSEC-2026-3929 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| huggingface | huggingface/transformers | unspecified – before 5.10.0 |
Weakness: CWE-22 · Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L