VulnerabilityAwaiting Analysis

CVE-2026-9856

A vulnerability in huggingface/transformers versions <=5.8.0.dev0 allows an attacker to perform arbitrary file writes via path traversal.

HIGH 7.1EPSS 0.29%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.29%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

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.

CVSS 3.0: 7.1 HIGHCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L
EPSS: 0.29% probability · 22th percentile
CISA KEV: Not listed
Weakness: CWE-22
Source: security@huntr.dev

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.