{"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":0.22371,"aliases":["GHSA-xrqw-3rrv-vx5w","PYSEC-2026-3929"],"ecosystem":"pip","vendor":"transformers","product":"transformers","affected":["transformers < 5.10.0"],"patched":["transformers 5.10.0"],"slug":"CVE-2026-9856","body":"## Overview\n\nA 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Package advisory (CVE-2026-9856)\n\nAffected packages:\n\n- `transformers < 5.10.0`\n\nPatched in:\n\n- `transformers 5.10.0`\n\nSource: https://osv.dev/vulnerability/GHSA-xrqw-3rrv-vx5w","depth":"twilight","depthScore":39,"depthScoreParts":{"impact":39.1,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}