---
title: "CVE-2026-87078: Net::IDN::Punycode - Denial of Service"
description: "Net::IDN::Punycode versions >= 2.302 and < 2.590 for Perl contain a memory leak caused by improper buffer release in decode_punycode XS backend, letting attackers cause memory exhaustion by sending invalid labels, exploit requires attacker to supply invalid labels."
url: https://panop.io/threat-heartbeat/CVE-2026-87078/
---

# CVE-2026-87078 Net::IDN::Punycode - Denial of Service

Net::IDN::Punycode versions >= 2.302 and < 2.590 for Perl contain a memory leak caused by improper buffer release in decode\_punycode XS backend, letting attackers cause memory exhaustion by sending invalid labels, exploit requires attacker to supply invalid labels.

CVSS base score 9.1 /10

Critical

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.39% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-87078)

## Details

Type

Denial of Service

Impact

Denial Of Service

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Published

22 September 2026

Updated

15 October 2026

Weakness

[CWE-401](https://cwe.mitre.org/data/definitions/401.html)

## Vendor fix

Update to version 2.590 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-87078](https://nvd.nist.gov/vuln/detail/CVE-2026-87078)
- [https://github.com/robrwo/Net-IDN-Encode/commit/edad63e0eeeeb18d93bc6dfe4d9dcdff9c244e1b.patch](https://github.com/robrwo/Net-IDN-Encode/commit/edad63e0eeeeb18d93bc6dfe4d9dcdff9c244e1b.patch)
- [https://metacpan.org/release/PJCJ/Net-IDN-Encode-2.590-TRIAL/changes](https://metacpan.org/release/PJCJ/Net-IDN-Encode-2.590-TRIAL/changes)
- [http://www.openwall.com/lists/oss-security/2026/09/22/13](http://www.openwall.com/lists/oss-security/2026/09/22/13)
- [https://github.com/robrwo/Net-IDN-Encode/commit/92572f726e48af5559de4cc8a831463b79dfb217.patch](https://github.com/robrwo/Net-IDN-Encode/commit/92572f726e48af5559de4cc8a831463b79dfb217.patch)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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