# 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.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 31 Aug 2026
- **Updated:** 1 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-19873, GHSA-8cjx-f34x-86x3, MGASA-2026-0404, UBUNTU-CVE-2026-19873

## 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.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-1284 (Improper Validation of Specified Quantity in Input)

## Which versions are affected by CVE-2026-19873?


## How do I fix CVE-2026-19873?

Apply the vendor's patch.

## Is CVE-2026-19873 being exploited?

There is no known exploitation of CVE-2026-19873 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-19873 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-19873 in the wild and no public exploit code.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-19873/ (Markdown: https://insights.sbomify.com/CVE-2026-19873/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-19873
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-19873
- OSV: https://osv.dev/vulnerability/CVE-2026-19873

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-19873/
Summaries are generated and may contain mistakes; the official description above is the record.