CVE-2026-74766

What it is

Net::IDN::Punycode versions from 2.301 before 2.590 for Perl allow a heap use-after-free via a decoded code point that reallocates the output buffer in decode_punycode. The XS backend inserts each decoded code point into the string buffer of the scalar it returns. decode_punycode computes the insertion pointer first and only then grows the buffer when the code point does not fit. The growth reallocates the buffer and updates every pointer except the insertion pointer, so the move that follows and the write of the code point go through a freed pointer. The buffer starts at twice the label length, and a code point above U+FFFF takes four bytes in the output, so a label of such code points outgrows it and forces the reallocation. Version 2.301, the fix for CVE-2016-15059, introduced the defect. Only the XS backend is affected. Decoding an attacker-supplied punycode label reads and writes freed heap memory.

At a glance

Exploitability

Can be exploited locally on the machine without logging in. High risk of data exposure, data tampering, service disruption.

Exploit odds

0.1% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-08-15 21:52 UTC ReservedThe CVE id was reserved by its CNA
2. 2026-09-22 08:16 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-09-22 19:07 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.1% in the next 30 days (EPSS).
• Severity: 8.4 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-09-22 08:16 UTC

Last modified

2026-09-22 19:07 UTC

Exploit probability

0.1% · EPSS, next 30 days

Weakness

CWE-416 · Use after free

Record status

Deferred

Attack profile CVSS 3.1 · 8.4

Attack vector

Local

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-74766.md and follow it. Check whether this project is affected by CVE-2026-74766. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

Copy as ticket · More options · Status badge