CVE-2026-9856
Path Traversal in huggingface/transformers
CVE-2026-9856 is a high vulnerability (CVSS 7.1) in Huggingface Huggingface/transformers, published August 2, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.46%, the 39th percentile. Fixed in transformers 5.10.0.
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- None
- Integrity
- High
- Availability
- Low
Exploit likelihood
What each source reports
CVE List Score used
7.1
Path Traversal in huggingface/transformers
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.
- Record
CVE-2026-9856- CVSS 3.0
- 7.1 High
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L - Weakness
- CWE-22
- Updated
- 2026-11-02
EUVDEUVD-2026-52005
7.1
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.
- Record
EUVD-2026-52005- CVSS 3.0
- 7.1 High
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-xrqw-3rrv-vx5w
7.1
Transformers save_pretrained path traversal allows arbitrary file writes through chat template names
A vulnerability in huggingface/transformers versions < 5.10.0 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.
- Record
GHSA-xrqw-3rrv-vx5w- CVSS 3.0
- 7.1 High
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L - Weakness
- CWE-22
- Updated
- 2026-11-02
NVD
7.1
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.
- Record
CVE-2026-9856- CVSS 3.0
- 7.1 High
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L - Weakness
- CWE-22
- Updated
- 2026-11-02
OSV
7.1
Path Traversal in huggingface/transformers
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.
- Record
CVE-2026-9856- CVSS 3.0
- 7.1 High
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L - Weakness
- CWE-22
- Updated
- 2026-11-02
OSVGHSA-xrqw-3rrv-vx5w
7.1
Transformers save_pretrained path traversal allows arbitrary file writes through chat template names
A vulnerability in huggingface/transformers versions < 5.10.0 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.
- Record
GHSA-xrqw-3rrv-vx5w- CVSS 3.0
- 7.1 High
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L - Weakness
- CWE-22
- Updated
- 2026-11-02
OSVPYSEC-2026-3929
7.1
Transformers save_pretrained path traversal allows arbitrary file writes through chat template names
A vulnerability in huggingface/transformers versions < 5.10.0 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.
- Record
PYSEC-2026-3929- CVSS 3.0
- 7.1 High
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L - Updated
- 2026-11-02
OSVCLSA-2026-1788512070 No score
TuxCare security update for transformers (1 CVE)
TuxCare rebuilt transformers to address 1 CVE. Fixed in 4.57.6.post4+tuxcare.
- Record
CLSA-2026-1788512070- Updated
- 2026-11-02
OSVROOT-APP-PYPI-CVE-2026-9856 No score
CVE-2026-9856 in transformers - Patched by Root
Root has patched CVE-2026-9856 in the transformers package for Root:PyPI. Multiple fixed versions available.
- Record
ROOT-APP-PYPI-CVE-2026-9856- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
transformersPyPI |
before 5.10.0 | 5.10.0 |
transformersTuxCare:PyPI |
4.57.6 up to 4.57.6.post4+tuxcare, plus listed versions 4.57.6.post1+tuxcare4.57.6.post2+tuxcare4.57.6.post3+tuxcare |
4.57.6.post4+tuxcare |
transformersPyPI |
before 5.10.0, plus listed versions 0.12.0.02.1.02.1.12.10.0 Show 45 moreShow less2.11.02.2.02.2.12.2.22.3.02.4.02.4.12.5.02.5.12.6.02.7.02.8.02.9.02.9.13.0.03.0.13.0.23.1.03.2.03.3.03.3.13.4.03.5.03.5.14.0.04.0.0rc14.0.14.1.04.1.14.10.04.10.14.10.24.10.34.11.04.11.14.11.24.11.34.12.04.12.14.12.24.12.34.12.44.12.54.13.04.14.0 |
5.10.0 |
transformersRoot:PyPI |
before 5.8.1+aikido.1 | 5.8.1+aikido.1 |
History
| When | Changed | Sources |
|---|---|---|
| 2026-11-02 | created | CVE List, EUVD, GitHub Advisories, NVD, OSV |
References
huntr.com/bounties/362824d5-fe18-40e8-a6cf-62277f97a170
github.com/huggingface/transformers/commit/eaaaf8494dd5386634ae37d1d122212fdc315be5
nvd.nist.gov/vuln/detail/CVE-2026-9856
github.com/huggingface/transformers/pull/46191
github.com/advisories/GHSA-xrqw-3rrv-vx5w
github.com/CVEProject/cvelistV5/tree/main/cves/2026/9xxx/CVE-2026-9856.json
github.com/huggingface/transformers
pypi.org/project/transformers
Left out here: 176 versions. The JSON record has them.