GHSA-xrqw-3rrv-vx5w: transformers (CVE-2026-9856)

Package	Ecosystem	Affected	Fixed in
transformers	PyPI	<5.10.0	5.10.0

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

The transformers package is vulnerable in versions before 5.10.0. The save_pretrained() methods of the tokenizer and processor base classes use keys from a chat_template dictionary directly as filenames without validation, so a crafted tokenizer_config.json from a malicious Hugging Face Hub repository can cause arbitrary file writes outside the save directory when a victim downloads and saves that tokenizer or processor. Upgrade to transformers 5.10.0 or later.

Written 1 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
7.1	High	3.0	CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L	CNA (@huntr_ai)

CISA KEV Not listed.
EPSS 0.0046, the 40th percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 14:10 UTC First seen by agentprime
31 Oct 2026, 14:10 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.