SEPTEMBER 20, 2026
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Case File

CVE-2026-9856

HIGH · CVSS 7.1 EPSS 0.29% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-08-02 · Last synced 2026-09-01

CyberRota Analysis

AI-Generated

The vulnerability allows arbitrary file writes due to improper validation of filenames in the `save_pretrained()` methods of certain classes in the huggingface/transformers library, specifically versions up to 5.8.0.dev0. Attackers can exploit this by crafting a malicious `tokenizer_config.json` file in a Hugging Face Hub repository, leading to potential compromise of the victim's file system. Organizations utilizing affected versions of the library, particularly those relying on the mentioned processors, should prioritize immediate remediation to mitigate this risk.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Detected Signals
exploit
GitHub PoC Links

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-9856
Severity
HIGH
CVSS
7.1
EPSS
0.29%

Original NVD 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.