CVE-2026-19872HTML::FormHandler versions before 0.410000 for Perl allow cross-site scripting via a submitted value rendered unescaped in an error message

Official description

HTML::FormHandler versions before 0.410000 for Perl allow cross-site scripting via a submitted value rendered unescaped in an error message. The wrappers and renderers that emit a form's errors interpolate the error string straight into HTML with no escaping. Two of the library's own messages, no_match and not_allowed, splice the submitted value into that string, and a failing type constraint puts the rejected value into the message it builds, which _apply_actions hands to add_error. A field declared with a check regexp, a check list or a type constraint reaches those messages, with no custom validator and no non-default configuration. Errors rendered through an application's own escaping template layer rather than the library's rendering roles are not affected. A request over the network that submits markup to such a field gets it back live inside the error span, running script in the victim's origin. Re-rendering a rejected value later gives the stored variant.

Affected packages & fixed versions

Affected products (as reported)

References

• https://github.com/gshank/html-formhandler/commit/2574fdb4561f5c32d44cfbfbb3188345d49eb5a2.patch patch
• https://metacpan.org/release/ABRAXXA/HTML-FormHandler-0.410000/changes release-notes
• http://www.openwall.com/lists/oss-security/2026/09/08/15