{"id":"CVE-2026-9856","summary":"Path Traversal in huggingface/transformers","details":"A vulnerability in huggingface/transformers versions \u003c=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.","modified":"2026-08-04T05:34:32.929366255Z","published":"2026-08-02T15:10:53.809Z","database_specific":{"cna_assigner":"@huntr_ai","cwe_ids":["CWE-22"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/9xxx/CVE-2026-9856.json","unresolved_ranges":[{"source":"AFFECTED_FIELD","extracted_events":[{"fixed":"5.10.0"}]}]},"references":[{"type":"WEB","url":"https://huntr.com/bounties/362824d5-fe18-40e8-a6cf-62277f97a170"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/9xxx/CVE-2026-9856.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-9856"},{"type":"FIX","url":"https://github.com/huggingface/transformers/commit/eaaaf8494dd5386634ae37d1d122212fdc315be5"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/huggingface/transformers","events":[{"introduced":"0"},{"fixed":"eaaaf8494dd5386634ae37d1d122212fdc315be5"}],"database_specific":{"source":"REFERENCES"}}],"versions":["v4.56.1-Vault-Gemma-preview","4.55.0-GLM-4.5V-preview-GLM-4.5V-preview","4.55.0-GLM-4.5V-preview","v4.53.2-Ernie-4.5-preview","v4.53.2-modernbert-decoder-preview","v4.52.4-Kyutai-STT-preview","v4.52.4-VJEPA-2-preview","v4.52.4-ColQwen2-preview","v4.51.3-CSM-preview","v4.51.3-GraniteMoeHybrid-preview","v4.51.3-LlamaGuard-preview","v4.51.3-D-FINE-preview","v4.51.3-SAM-HQ-preview","v4.51.3-BitNet-preview","v4.51.3-InternVL-preview","v4.51.3-Janus-preview","v4.51.3-TimesFM-preview","v4.51.3-MLCD-preview","v4.51.3-Qwen2.5-Omni-preview","v4.50.3-DeepSeek-3","v4.49.0-Mistral-3","v4.49.0-AyaVision","v4.49.0-SigLIP-2","v4.49.0-SmolVLM-2","v4.33.1","v4.16.0","v4.15.0","v4.14.0","v4.13.0","v4.12.0","v4.11.0","v4.10.0","v4.9.0","v4.8.0","v4.7.0","v4.6.0","v4.5.0","v4.4.0","v4.3.0.rc1","4.3.0.rc1","v4.2.0","v4.1.1","v4.1.0","v3.5.0","v3.4.0","v3.3.1","v3.3.0","v3.2.0","v3.1.0","v3.0.2","v3.0.1","3.0.1","v3.0.0","v2.11.0","v2.10.0","v2.9.1","v2.9.0","v2.8.0","v2.7.0","v2.6.0","v2.5.1","v2.5.0","v2.4.1","v2.4.0","v2.3.0","v2.2.2","v2.2.1","v2.2.0","v2.1.1","v2.1.0","v2.0.0","1.2.0","1.1.0","1.0","v0.6.2","v0.6.1","v0.6.0","v0.5.1","v0.5.0","0.5.0","v0.4.0","v0.3.0","v0.2.0","v0.1.2","0.1.2"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-9856.json"}}],"schema_version":"1.8.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L"}]}