CVE-2026-66296

Summary

Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in lud oaskit allows reflected cross-site scripting via the default HTML error handler.

Oaskit.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.

Because 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[</code></h2><script>alert(document.domain)</script>]=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.

Both 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.

This issue affects oaskit: from 0.1.0 before 0.14.1.

Affected Software

VendorProductVersion RangeStatus
ludoaskit0.1.0 < 0.14.1affected
ludoaskit552de8ca0ff60617bea58bcafa451892d61a161c < b70c6b2eaf0b11bdd0bbb21b8a87dbb3d46918a1affected

Weaknesses

  • CWE-79: CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Workarounds

Disable HTML error rendering so that validation failures are returned as JSON only:

plug Oaskit.Plugs.ValidateRequest, html_errors: false

This prevents the vulnerable HTML page from being rendered at all, on any oaskit version. Alternatively, configure a custom :error_handler that does not emit HTML built from request-derived values.

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: poc
    • Automatable: no
    • Technical Impact: partial

Additional References

References