{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "5.36"
              }
            ],
            "source": [
              "DESCRIPTION",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "b265e58bb1ead8133eb7614b76bb7891bd96cea0"
            },
            {
              "fixed": "956619a9e94f86d8d2c529b4e06a3674c54a73e7"
            }
          ],
          "repo": "https://github.com/libwww-perl/uri",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "CPANSec",
    "cwe_ids": [
      "CWE-1289"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/19xxx/CVE-2026-19953.json"
  },
  "details": "URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep.\n\nnameprep lowercases each host label but performs no Unicode normalization. IDNA requires a label to be normalized to Form C before it is encoded (RFC 5891), so a label that is not already in NFC is encoded to a different A-label than its normalized form. A label built from the precomposed Devanagari sequence U+0958 U+093E encodes to xn--72b5c without normalization but to xn--11b2fg after NFC normalization, and xn--72b5c does not round-trip back to the original label.\n\nAny caller that reads host() from a URI built from untrusted input and uses it for a security decision (an allow or deny list, an SSRF filter, deduplication, a cache key) sees the non-standard label, while a client that fetches the same URL resolves the NFC form, so the check and the fetch can disagree about the host.",
  "id": "CVE-2026-19953",
  "modified": "2026-09-02T03:30:29.316282631Z",
  "published": "2026-08-31T17:29:42.929Z",
  "references": [
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2026/08/31/14"
    },
    {
      "type": "WEB",
      "url": "https://cpan.org/modules"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/19xxx/CVE-2026-19953.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://metacpan.org/release/OALDERS/URI-5.36/changes"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-19953"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/libwww-perl/URI/pull/191"
    },
    {
      "type": "FIX",
      "url": "https://github.com/libwww-perl/URI/commit/956619a9e94f86d8d2c529b4e06a3674c54a73e7.patch"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/libwww-perl/URI"
    },
    {
      "type": "ARTICLE",
      "url": "https://www.rfc-editor.org/rfc/rfc5891#section-5.2"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep"
}