{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0.1.0"
              },
              {
                "fixed": "0.14.1"
              }
            ],
            "source": [
              "DESCRIPTION",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "3ca707778b796488d8054c29d31043bc1e3f66e2"
            },
            {
              "fixed": "37f1b7df9d9fd9d0bc3d69ad4759f3c71b174e3b"
            },
            {
              "fixed": "b70c6b2eaf0b11bdd0bbb21b8a87dbb3d46918a1"
            }
          ],
          "repo": "https://github.com/lud/oaskit",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-h7xw-x8wr-xpcc"
  ],
  "database_specific": {
    "cna_assigner": "EEF",
    "cwe_ids": [
      "CWE-79"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66296.json",
    "unresolved_ranges": [
      {
        "extracted_events": [
          {
            "introduced": "552de8ca0ff60617bea58bcafa451892d61a161c"
          },
          {
            "fixed": "b70c6b2eaf0b11bdd0bbb21b8a87dbb3d46918a1"
          }
        ],
        "source": "AFFECTED_FIELD"
      }
    ]
  },
  "details": "Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in lud oaskit allows reflected cross-site scripting via the default HTML error handler.\n\nOaskit.ErrorHandler.Default.format_reason/4 and Oaskit.ErrorHandler.Default.reason_to_html/1 in lib/oaskit/error_handler/default.ex render request-validation failures as an HTML page whenever the request's Accept header contains html, interpolating request-controlled strings into that page without HTML escaping. The unescaped values are object keys taken from a request body or from an object or deepObject query parameter, which appear in the JSON Schema error's instance path when a schema rejects them (for example under additionalProperties: false), and the raw Content-Type header, reflected in unsupported-media-type errors when it fails to parse.\n\nBecause browsers send Accept: text/html on ordinary top-level navigation, a crafted GET link is sufficient to trigger the error page; no form submission, custom Content-Type, or attacker-controlled script on the victim's side is required. A payload such as filter[\u003c/code\u003e\u003c/h2\u003e\u003cscript\u003ealert(document.domain)\u003c/script\u003e]=x terminates the enclosing markup and the injected script executes in the origin of the application using oaskit, giving it access to that origin's cookies, session, and same-origin responses.\n\nBoth HTML error rendering and the vulnerable handler are enabled by default: Oaskit.Plugs.ValidateRequest defaults :html_errors to true and :error_handler to Oaskit.ErrorHandler.Default, so applications following the documented usage are affected without any opt-in.\n\nThis issue affects oaskit: from 0.1.0 before 0.14.1.",
  "id": "CVE-2026-66296",
  "modified": "2026-08-06T03:30:58.627949266Z",
  "published": "2026-08-03T19:04:30.556Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://cna.erlef.org/cves/CVE-2026-66296.html"
    },
    {
      "type": "WEB",
      "url": "https://github.com"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-66296"
    },
    {
      "type": "WEB",
      "url": "https://repo.hex.pm"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66296.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/lud/oaskit/security/advisories/GHSA-h7xw-x8wr-xpcc"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-66296"
    },
    {
      "type": "FIX",
      "url": "https://github.com/lud/oaskit/commit/b70c6b2eaf0b11bdd0bbb21b8a87dbb3d46918a1"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lud/oaskit"
    }
  ],
  "schema_version": "1.8.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Reflected XSS in oaskit's default HTML error handler"
}