{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "last_affected": "0.23.2"
              }
            ],
            "source": "AFFECTED_FIELD"
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "88a4498ad4ea1a9487b0a9b0ff881383fd5a06a3"
            }
          ],
          "repo": "https://github.com/huggingface/tokenizers",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "VulnCheck",
    "cwe_ids": [
      "CWE-787"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/85xxx/CVE-2026-85670.json"
  },
  "details": "tokenizers (Hugging Face) is affected by an out-of-bounds buffer access in BpeBuilder::build (tokenizers/src/models/bpe/model.rs). When loading a tokenizer.json via Tokenizer::from_file/from_str, the builder sizes a scratch buffer to the longest vocabulary key, then writes each concatenated merge rule into it. A merge whose concatenated token exceeds the longest vocabulary key overruns the buffer, which Rust turns into a panic that aborts the process in Rust and FFI embeddings. This occurs at load time with no encoding required, so an attacker who supplies a crafted tokenizer.json can cause a denial of service. A secondary defect at the same location can cause a usize underflow (panic in debug, potential memory corruption in release) when continuing_subword_prefix is set and a merge token is shorter than the prefix. Observed in version 0.23.1.",
  "id": "CVE-2026-85670",
  "modified": "2026-09-06T03:30:43.180102675Z",
  "published": "2026-09-04T14:32:25.391Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/85xxx/CVE-2026-85670.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-85670"
    },
    {
      "type": "ADVISORY",
      "url": "https://www.vulncheck.com/advisories/tokenizers-bpebuilder-buffer-overflow-via-merge-token"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/huggingface/tokenizers/issues/2094"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/huggingface/tokenizers"
    },
    {
      "type": "ARTICLE",
      "url": "https://github.com/huggingface/tokenizers/blob/v0.23.2/tokenizers/src/models/bpe/model.rs"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "tokenizers BpeBuilder Buffer Overflow via merge token"
}