{
  "affected": [
    {
      "package": {
        "ecosystem": "RubyGems",
        "name": "nokogiri"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.19.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-06T18:24:18Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "## Summary\n\nNokogiri\u0027s CSS selector tokenizer contains regular expressions whose construction may result in exponential regex backtracking on adversarial selectors. Three ReDoS vectors are addressed in this release:\n\n1. String-literal tokenization on certain unterminated quoted-string input.\n2. String-literal tokenization on a separate class of hex-escape-rich input.\n3. Identifier tokenization on hex-escape-rich input.\n\nThe public CSS selector methods that funnel through the affected tokenizer are `Nokogiri::CSS.xpath_for`, `Node#css`, `Node#at_css`, `Searchable#search`, and `CSS::Parser#parse`.\n\n\n## Mitigation\n\nUpgrade to Nokogiri `\u003e= 1.19.3`.\n\nIf users are unable to upgrade, two options are available:\n\n- Avoid the use of attacker-controlled text in CSS selectors. Applications that only pass developer-authored selectors to Nokogiri are not directly exposed.\n- Set global `Regexp.timeout` (Ruby 3.2+, JRuby 9.4+) to bound parse time.\n\n## Severity\n\nThe Nokogiri maintainers have evaluated this as **High Severity** (CVSS 7.5, `AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`).\n\nAn attacker able to inject user-supplied text into a CSS selector parse method can cause exponential backtracking, resulting in a potential denial of service.\n\n\n## Resources\n\n- [CWE-1333: Inefficient Regular Expression Complexity](https://cwe.mitre.org/data/definitions/1333.html)\n\n\n## Credit\n\nVector 1 was responsibly reported by @colby-swandale. Vectors 2 and 3 were discovered by @flavorjones during the response to the original report.",
  "id": "GHSA-c4rq-3m3g-8wgx",
  "modified": "2026-05-06T18:24:18Z",
  "published": "2026-05-06T18:24:18Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/sparklemotion/nokogiri/security/advisories/GHSA-c4rq-3m3g-8wgx"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/sparklemotion/nokogiri"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Nokogiri CSS selector tokenizer has regular expression backtracking"
}