---
id: CVE-2026-87081
title: >-
  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
  lim…
summary: >-
  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
  lim…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-407
product: Net-IDN-Encode
affected:
  - Net-IDN-Encode < 2.590
published: '2026-09-22'
updated: '2026-09-22'
sourceUpdated: '2026-09-22T19:07:00.983'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-87081'
references:
  - url: >-
      https://github.com/robrwo/Net-IDN-Encode/commit/5ac3315131264670efcd3a29857b651506dfee8e.patch
    label: 9b29abf9-4ab0-4765-b253-1875cd9b441e
  - url: >-
      https://github.com/robrwo/Net-IDN-Encode/commit/ea34f812d7dc67f3b211f4d92e74c6a7e24d764a.patch
    label: 9b29abf9-4ab0-4765-b253-1875cd9b441e
  - url: 'https://metacpan.org/release/PJCJ/Net-IDN-Encode-2.590-TRIAL/changes'
    label: 9b29abf9-4ab0-4765-b253-1875cd9b441e
  - url: 'http://www.openwall.com/lists/oss-security/2026/09/22/16'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
  - cve.org
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-22T15:18:17.110980Z'
ingestedAt: '2026-09-22T08:00:27.698Z'
epss: 0.0063
epssPercentile: 0.47958
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.