Vulnerability-Lookup

PYSEC-2026-3929

Vulnerability from pysec - Published: 2026-09-10 09:44 - Updated: 2026-09-10 11:02

Details

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.

Severity

7.1 (High)


                  
                    CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L

Impacted products

Name	purl
transformers	pkg:pypi/transformers

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "transformers",
        "purl": "pkg:pypi/transformers"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "5.10.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.1",
        "2.0.0",
        "2.1.0",
        "2.1.1",
        "2.10.0",
        "2.11.0",
        "2.2.0",
        "2.2.1",
        "2.2.2",
        "2.3.0",
        "2.4.0",
        "2.4.1",
        "2.5.0",
        "2.5.1",
        "2.6.0",
        "2.7.0",
        "2.8.0",
        "2.9.0",
        "2.9.1",
        "3.0.0",
        "3.0.1",
        "3.0.2",
        "3.1.0",
        "3.2.0",
        "3.3.0",
        "3.3.1",
        "3.4.0",
        "3.5.0",
        "3.5.1",
        "4.0.0",
        "4.0.0rc1",
        "4.0.1",
        "4.1.0",
        "4.1.1",
        "4.10.0",
        "4.10.1",
        "4.10.2",
        "4.10.3",
        "4.11.0",
        "4.11.1",
        "4.11.2",
        "4.11.3",
        "4.12.0",
        "4.12.1",
        "4.12.2",
        "4.12.3",
        "4.12.4",
        "4.12.5",
        "4.13.0",
        "4.14.0",
        "4.14.1",
        "4.15.0",
        "4.16.0",
        "4.16.1",
        "4.16.2",
        "4.17.0",
        "4.18.0",
        "4.19.0",
        "4.19.1",
        "4.19.2",
        "4.19.3",
        "4.19.4",
        "4.2.0",
        "4.2.1",
        "4.2.2",
        "4.20.0",
        "4.20.1",
        "4.21.0",
        "4.21.1",
        "4.21.2",
        "4.21.3",
        "4.22.0",
        "4.22.1",
        "4.22.2",
        "4.23.0",
        "4.23.1",
        "4.24.0",
        "4.25.0",
        "4.25.1",
        "4.26.0",
        "4.26.1",
        "4.27.0",
        "4.27.1",
        "4.27.2",
        "4.27.3",
        "4.27.4",
        "4.28.0",
        "4.28.1",
        "4.29.0",
        "4.29.1",
        "4.29.2",
        "4.3.0",
        "4.3.0rc1",
        "4.3.1",
        "4.3.2",
        "4.3.3",
        "4.30.0",
        "4.30.1",
        "4.30.2",
        "4.31.0",
        "4.32.0",
        "4.32.1",
        "4.33.0",
        "4.33.1",
        "4.33.2",
        "4.33.3",
        "4.34.0",
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        "4.35.1",
        "4.35.2",
        "4.36.0",
        "4.36.1",
        "4.36.2",
        "4.37.0",
        "4.37.1",
        "4.37.2",
        "4.38.0",
        "4.38.1",
        "4.38.2",
        "4.39.0",
        "4.39.1",
        "4.39.2",
        "4.39.3",
        "4.4.0",
        "4.4.1",
        "4.4.2",
        "4.40.0",
        "4.40.1",
        "4.40.2",
        "4.41.0",
        "4.41.1",
        "4.41.2",
        "4.42.0",
        "4.42.1",
        "4.42.2",
        "4.42.3",
        "4.42.4",
        "4.43.0",
        "4.43.1",
        "4.43.2",
        "4.43.3",
        "4.43.4",
        "4.44.0",
        "4.44.1",
        "4.44.2",
        "4.45.0",
        "4.45.1",
        "4.45.2",
        "4.46.0",
        "4.46.1",
        "4.46.2",
        "4.46.3",
        "4.47.0",
        "4.47.1",
        "4.48.0",
        "4.48.1",
        "4.48.2",
        "4.48.3",
        "4.49.0",
        "4.5.0",
        "4.5.1",
        "4.50.0",
        "4.50.1",
        "4.50.2",
        "4.50.3",
        "4.51.0",
        "4.51.1",
        "4.51.2",
        "4.51.3",
        "4.52.0",
        "4.52.1",
        "4.52.2",
        "4.52.3",
        "4.52.4",
        "4.53.0",
        "4.53.1",
        "4.53.2",
        "4.53.3",
        "4.54.0",
        "4.54.1",
        "4.55.0",
        "4.55.1",
        "4.55.2",
        "4.55.3",
        "4.55.4",
        "4.56.0",
        "4.56.1",
        "4.56.2",
        "4.57.0",
        "4.57.1",
        "4.57.2",
        "4.57.3",
        "4.57.4",
        "4.57.5",
        "4.57.6",
        "4.6.0",
        "4.6.1",
        "4.7.0",
        "4.8.0",
        "4.8.1",
        "4.8.2",
        "4.9.0",
        "4.9.1",
        "4.9.2",
        "5.0.0",
        "5.0.0rc0",
        "5.0.0rc1",
        "5.0.0rc2",
        "5.0.0rc3",
        "5.1.0",
        "5.2.0",
        "5.3.0",
        "5.4.0",
        "5.5.0",
        "5.5.1",
        "5.5.2",
        "5.5.3",
        "5.5.4",
        "5.6.0",
        "5.6.1",
        "5.6.2",
        "5.7.0",
        "5.8.0",
        "5.8.1",
        "5.9.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-9856",
    "GHSA-xrqw-3rrv-vx5w"
  ],
  "details": "A vulnerability in huggingface/transformers versions \u003c 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.",
  "id": "PYSEC-2026-3929",
  "modified": "2026-09-10T11:02:34.656018Z",
  "published": "2026-09-10T09:44:51.053247Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-9856"
    },
    {
      "type": "WEB",
      "url": "https://github.com/huggingface/transformers/pull/46191"
    },
    {
      "type": "WEB",
      "url": "https://github.com/huggingface/transformers/commit/eaaaf8494dd5386634ae37d1d122212fdc315be5"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/huggingface/transformers"
    },
    {
      "type": "WEB",
      "url": "https://huntr.com/bounties/362824d5-fe18-40e8-a6cf-62277f97a170"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/transformers"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-xrqw-3rrv-vx5w"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Transformers save_pretrained path traversal allows arbitrary file writes through chat template names"
}

CVE-2026-9856 (GCVE-0-2026-9856)

Vulnerability from cvelistv5 – Published: 2026-08-02 15:10 – Updated: 2026-08-03 14:57

Title

Path Traversal in huggingface/transformers

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.

Severity

7.1 (High)


                        
                          CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-03 14:57 UTC

CWE

CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

Assigner

@huntr_ai mitre root

References

2 references

URL	Tags
https://huntr.com/bounties/362824d5-fe18-40e8-a6c…
https://github.com/huggingface/transformers/commi…

Impacted products

1 product

Vendor	Product	Version
huggingface	huggingface/transformers	Affected: unspecified , < 5.10.0 (custom)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-9856",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-03T14:57:31.978427Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-03T14:57:43.370Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "huggingface/transformers",
          "vendor": "huggingface",
          "versions": [
            {
              "lessThan": "5.10.0",
              "status": "affected",
              "version": "unspecified",
              "versionType": "custom"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "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."
        }
      ],
      "metrics": [
        {
          "cvssV3_0": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L",
            "version": "3.0"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-22",
              "description": "CWE-22 Improper Limitation of a Pathname to a Restricted Directory (\u0027Path Traversal\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-02T15:10:53.809Z",
        "orgId": "c09c270a-b464-47c1-9133-acb35b22c19a",
        "shortName": "@huntr_ai"
      },
      "references": [
        {
          "url": "https://huntr.com/bounties/362824d5-fe18-40e8-a6cf-62277f97a170"
        },
        {
          "url": "https://github.com/huggingface/transformers/commit/eaaaf8494dd5386634ae37d1d122212fdc315be5"
        }
      ],
      "source": {
        "advisory": "362824d5-fe18-40e8-a6cf-62277f97a170",
        "discovery": "EXTERNAL"
      },
      "title": "Path Traversal in huggingface/transformers"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "c09c270a-b464-47c1-9133-acb35b22c19a",
    "assignerShortName": "@huntr_ai",
    "cveId": "CVE-2026-9856",
    "datePublished": "2026-08-02T15:10:53.809Z",
    "dateReserved": "2026-05-28T15:41:24.076Z",
    "dateUpdated": "2026-08-03T14:57:43.370Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

GHSA-XRQW-3RRV-VX5W

Vulnerability from github – Published: 2026-08-02 18:30 – Updated: 2026-09-01 18:58

Summary

Transformers save_pretrained path traversal allows arbitrary file writes through chat template names

Details

Severity

7.1 (High)


                  
                    CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "transformers"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "5.10.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-9856"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-22"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-01T18:58:08Z",
    "nvd_published_at": "2026-08-02T16:16:25Z",
    "severity": "HIGH"
  },
  "details": "A vulnerability in huggingface/transformers versions \u003c 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.",
  "id": "GHSA-xrqw-3rrv-vx5w",
  "modified": "2026-09-01T18:58:08Z",
  "published": "2026-08-02T18:30:20Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-9856"
    },
    {
      "type": "WEB",
      "url": "https://github.com/huggingface/transformers/pull/46191"
    },
    {
      "type": "WEB",
      "url": "https://github.com/huggingface/transformers/commit/eaaaf8494dd5386634ae37d1d122212fdc315be5"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/huggingface/transformers"
    },
    {
      "type": "WEB",
      "url": "https://huntr.com/bounties/362824d5-fe18-40e8-a6cf-62277f97a170"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Transformers save_pretrained path traversal allows arbitrary file writes through chat template names"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

PYSEC-2026-3929

CVE-2026-9856 (GCVE-0-2026-9856)

GHSA-XRQW-3RRV-VX5W

Tags

Sightings

Nomenclature