---
id: CVE-2026-9856
title: >-
  A vulnerability in huggingface/transformers versions <=5.8.0.dev0 allows an
  attacker to perform arbitrary file writes via path traversal
summary: >-
  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
  `ProcessorMix…
severity: high
cvss: 7.1
cvssVector: 'CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L'
cwe:
  - CWE-22
published: '2026-08-02'
updated: '2026-08-02'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-9856'
references:
  - url: >-
      https://github.com/huggingface/transformers/commit/eaaaf8494dd5386634ae37d1d122212fdc315be5
    label: security@huntr.dev
  - url: 'https://huntr.com/bounties/362824d5-fe18-40e8-a6cf-62277f97a170'
    label: security@huntr.dev
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-9856'
  - url: 'https://github.com/huggingface/transformers/pull/46191'
  - url: 'https://github.com/huggingface/transformers'
  - url: 'https://pypi.org/project/transformers'
  - url: 'https://github.com/advisories/GHSA-xrqw-3rrv-vx5w'
tags:
  - nvd
  - osv
  - pip
ingestedAt: '2026-08-02T16:18:42.489Z'
epss: 0.00295
epssPercentile: 0.22375
aliases:
  - GHSA-xrqw-3rrv-vx5w
  - PYSEC-2026-3929
ecosystem: pip
vendor: transformers
product: transformers
affected:
  - transformers < 5.10.0
patched:
  - transformers 5.10.0
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-9856)

Affected packages:

- `transformers < 5.10.0`

Patched in:

- `transformers 5.10.0`

Source: https://osv.dev/vulnerability/GHSA-xrqw-3rrv-vx5w