# CVE-2026-87081: libnet-idn-encode-perl: Net::IDN::UTS46 versions before 2.590 for Perl allow CPU exhaustion via quadratic punycode encoding of an overlong la...

CVE-2026-87081 is fixed in 4 products on 1 platform, first by DEBIAN-CVE-2026-87081, released September 22, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-87081
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0038
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 22, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libnet-idn-encode-perl Debian 14 | 2.600-1 | [DEBIAN-CVE-2026-87081](https://patchblox.com/security/data/fix/linux/debian-cve-2026-87081.md) | Sep 22, 2026 |
| Linux | perl-Net-IDN-Encode amzn 2023 | 2.590-1.amzn2023.0.1 | [ALAS2023-2026-3190](https://patchblox.com/security/data/fix/linux/alas2023-2026-3190.md) | Nov 7, 2026 |
| Linux | perl-Net-IDN-Encode-debuginfo amzn 2023 | 2.590-1.amzn2023.0.1 | [ALAS2023-2026-3190](https://patchblox.com/security/data/fix/linux/alas2023-2026-3190.md) | Nov 7, 2026 |
| Linux | perl-Net-IDN-Encode-debugsource amzn 2023 | 2.590-1.amzn2023.0.1 | [ALAS2023-2026-3190](https://patchblox.com/security/data/fix/linux/alas2023-2026-3190.md) | Nov 7, 2026 |

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Data as of 2026-11-10T01:44:33Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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