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Fencer Intel
high 7.1

CVE-2026-9856 json

Path Traversal in huggingface/transformers

published 3mo ago modified 19d ago also GHSA-xrqw-3rrv-vx5w , PYSEC-2026-3929 , EUVD-2026-52005

cvss
7.1
version 3.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 40%
public exploits
0
none known

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 `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.

Patch / fix

  • pypi transformers 5.10.0
  • huggingface huggingface/transformers 5.10.0

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-9856 updated cvss 8.1

transformers: Hugging Face Transformers: Arbitrary file write via path traversal

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3mo ago

Exploit prediction

0.46% chance of exploitation in the next 30 days, higher than 40% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.0 7.1 CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L
OSV 3.0 7.1 CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L
GitHub 3.0 7.1 CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L

Affected packages

ecosystem package affected fixed in
pypi transformers
<5.10.0
5.10.0

Affected products

  • huggingface huggingface/transformers

Classification

Weakness
  • CWE-22 Improper Limitation of a Pathname to a Restricted Directory

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.