CVE-2026-9856

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 v3 7.1 HIGH

7.1^/10

CVSS v3 : HIGH

Vector : AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L

Exploitability : 2.8 / Impact : 4.2

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction REQUIRED

Confidentiality Impact NONE

Integrity Impact HIGH

Availability Impact LOW

Scope UNCHANGED

References

Link	Resource
https://github.com/huggingface/transformers/commit/eaaaf8494dd5386634ae37d1d122212fdc315be5
https://huntr.com/bounties/362824d5-fe18-40e8-a6cf-62277f97a170

Configurations

No configuration.

History

02 Aug 2026, 16:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-08-02 16:16

Updated : 2026-08-03 16:16

NVD link : CVE-2026-9856

Mitre link : CVE-2026-9856

CVE.ORG link : CVE-2026-9856

JSON object : View

Products Affected

No product.

CWE

CWE-22

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

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