CVE-2026-19873 HTML::FormFu versions through 2.08 for Perl allow resource exhaustion via an unbounded repeat count from the query string in Repeatable elements.
Attackers can cause denial of service in Perl applications using HTML::FormFu by sending unbounded repeat counts in query strings, exhausting memory and CPU.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-19873?
CVE-2026-19873 is a high-severity denial of service vulnerability, published on 31 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
HTML::FormFu versions through 2.08 for Perl allow resource exhaustion via an unbounded repeat count from the query string in Repeatable elements.
When a Repeatable element has counter_name set, its process method reads the repeat count from the named query string parameter, checks only that it is a positive integer, and passes it to repeat, which deep-clones the element's child subtree once per iteration. Nothing caps the value, and no attribute lets an application impose a limit.
The count is read on every request, before the form decides whether it was submitted, so a plain GET reaches the clone loop with no credentials, no session and no request body. Nesting multiplies: a Repeatable inside a Repeatable takes a counter at each level, so an outer and an inner value of 100 build 10,000 clones.
Once the form is submitted, each cloned field's constraints scan the whole element tree in _find_field_value, so cost grows faster than linearly with the count. A single request exhausts memory and CPU.
The latest release on CPAN is 2.07, from 2018. Version 2.08 exists only in the git repository.
Which versions are affected by CVE-2026-19873?
How do I fix CVE-2026-19873?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-19873 being exploited?
There is no known exploitation of CVE-2026-19873 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-19873, GHSA-8cjx-f34x-86x3, MGASA-2026-0404, UBUNTU-CVE-2026-19873.