Regular Expression Denial of Service (ReDoS) in huggingface/transformers

{
  "id": "fbf34c1f6afafbdf86077c14ec9dbb1fc4dab4fc8cad7328b4fd15fad0618cbc",
  "url": "https://osv.dev/vulnerability/CVE-2025-6921",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Regular Expression Denial of Service (ReDoS) in huggingface/transformers",
    "summary": "The huggingface/transformers library, versions prior to 4.53.0, is vulnerable to Regular Expression Denial of Service (ReDoS) in the AdamWeightDecay optimizer. The vulnerability arises from the _do_use_weight_decay method, which processes user-controlled regular expressions in the include_in_weight_decay and exclude_from_weight_decay lists. Malicious regular expressions can cause catastrophic backtracking during the re.search call, leading to 100% CPU utilization and a denial of service. This issue can be exploited by attackers who can control the patterns in these lists, potentially causing the machine learning task to hang and rendering services unresponsive.",
    "evidence": "osv:CVE-2025-6921",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2025-6921",
      "aliases": [
        "CVE-2025-6921",
        "GHSA-4w7r-h757-3r74",
        "PYSEC-2026-1980"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/huggingface/transformers",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "67ddc82fbc7e52c6f42a395b4a6d278c55b77a39"
                },
                {
                  "fixed": "47c34fba5c303576560cb29767efb452ff12b8be"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:huggingface:transformers:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "4.53.0"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "47c34fba5c303576560cb29767efb452ff12b8be"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "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-2025-6921.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:25.931791389Z",
      "provider": "osv",
      "references": [
        "https://huntr.com/bounties/287d15a7-6e7c-45d2-8c05-11e305776f1f",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/6xxx/CVE-2025-6921.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-6921",
        "https://github.com/huggingface/transformers/commit/47c34fba5c303576560cb29767efb452ff12b8be"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-400"
        ],
        "cna_assigner": "@huntr_ai",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/6xxx/CVE-2025-6921.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-6921",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 492339,
  "published_at": "2025-09-23T13:56:15.636+00:00"
}