# CVE-2026-87081: Net::IDN::UTS46 versions before 2.590 for Perl allow CPU exhaustion via quadratic punycode encoding of an overlong label before the length check in to_ascii.

> Attackers can cause CPU exhaustion in Perl applications using Net::IDN::UTS46 by submitting overlong labels with distinct non-ASCII characters.

- **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:** No
- **Published:** 22 Sep 2026
- **Updated:** 22 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-87081, GHSA-653x-rhrr-h9h8, UBUNTU-CVE-2026-87081

## What is CVE-2026-87081?

CVE-2026-87081 is a high-severity denial of service vulnerability, published on 22 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Net::IDN::UTS46 versions before 2.590 for Perl allow CPU exhaustion via quadratic punycode encoding of an overlong label before the length check in to_ascii.

to_ascii punycode encodes each label and only then applies the 63-byte DNS limit. encode_punycode in both backends follows the sample implementation in RFC 3492, whose outer loop runs once per distinct non-ASCII code point and scans the whole input each round, so a label of distinct non-ASCII characters costs the square of its length before the limit rejects it. Every ASCII conversion in the distribution, including domain_to_ascii and email_to_ascii, goes through to_ascii.

Weakness: CWE-407 (Inefficient Algorithmic Complexity)

## Which versions are affected by CVE-2026-87081?


## How do I fix CVE-2026-87081?

No fix has been published for CVE-2026-87081 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-87081 being exploited?

There is no known exploitation of CVE-2026-87081 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-87081 and fix it if it is affected.

What it is: CVE-2026-87081 is a high-severity denial of service vulnerability, published on 22 Sep 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-2026-87081 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-2026-87081/ (Markdown: https://insights.sbomify.com/CVE-2026-87081/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-87081
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-87081
- OSV: https://osv.dev/vulnerability/CVE-2026-87081

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-87081/
Summaries are generated and may contain mistakes; the official description above is the record.