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CVE-2026-19872: HTML::FormHandler <0.410000 can run script in error output

CVE-2026-19872 · published 1 month ago

Summary

Versions of the HTML::FormHandler Perl library older than 0.410000 may show a user‑submitted value in an error message without cleaning it first. An attacker who sends a crafted form can make the malicious code appear in the page, potentially executing in the user’s browser. Upgrade to version 0.410000 or later, or ensure that error messages are properly escaped before being displayed.

What to do

Update debian libhtml-formhandler-perl to version 0.410002-1.

Affected software

Ecosystem	Vendor	Product	Affected versions
Debian:12	debian	libhtml-formhandler-perl	All versions
Ubuntu:16.04:LTS	canonical	libhtml-formhandler-perl	All versions
Debian:14	debian	libhtml-formhandler-perl	< 0.410002-1 Fix: upgrade to 0.410002-1

Original advisory text

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

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.

References

https://security-tracker.debian.org/tracker/CVE-2026-19872 Vendor Advisory
http://www.openwall.com/lists/oss-security/2026/09/08/15 URL
https://metacpan.org/release/ABRAXXA/HTML-FormHandler-0.410000/changes Vendor Advisory
https://cpan.org/modules URL
https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/19xxx/CVE-2026-19872... Vendor Advisory
https://nvd.nist.gov/vuln/detail/CVE-2026-19872 Vendor Advisory
https://github.com/gshank/html-formhandler Product
https://ubuntu.com/security/CVE-2026-19872 Third Party Advisory
https://www.cve.org/CVERecord?id=CVE-2026-19872 Third Party Advisory
https://lists.security.metacpan.org/cve-announce/msg/43387502/ Third Party Advisory
https://github.com/gshank/html-formhandler/commit/2574fdb4561f5c32d44cfbfbb31883... Patch

Fix within

Internet-facing 60 days

Internal At next upgrade

Not known to be exploited
Needs hands-on effort to exploit
Gives an attacker partial control

Severity

6.1 Medium

Exploitation

<1% chance of attack within 30 days

Type

CWE-79Cross-site Scripting (XSS)

Timeline

Published8 Sep 2026

Updated31 Oct 2026

First seen8 Sep 2026

Sources

CVE-2026-19872 · NVD

CVE-2026-19872 · MITRE

DEBIAN-CVE-2026-19872 · OSV

UBUNTU-CVE-2026-19872 · OSV

CVE-2026-19872 · OSV

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