Description
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.
Published: 2026-09-22
Score: 8.4 High
EPSS: < 1% Very Low
KEV: No
AI Analysis

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Remediation

Vendor Solution

Upgrade to Net-IDN-Encode 2.590-TRIAL or later.

Tracking

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Advisories

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History

Tue, 29 Sep 2026 13:30:00 +0000

Type Values Removed Values Added
First Time appeared Perl
Perl net::idn::punycode
Vendors & Products Perl
Perl net::idn::punycode

Tue, 22 Sep 2026 13:30:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 8.4, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Tue, 22 Sep 2026 07:30:00 +0000

Type Values Removed Values Added
Description 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.
Title 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
Weaknesses CWE-416
References

Subscriptions

Perl Net::idn::punycode
cve-icon MITRE

Status: PUBLISHED

Assigner: CPANSec

Published:

Updated: 2026-09-22T12:41:52.010Z

Reserved: 2026-08-15T21:52:57.406Z

Link: CVE-2026-74766

cve-icon Vulnrichment

Updated: 2026-09-22T12:40:37.148Z

cve-icon NVD

Status : Deferred

Published: 2026-09-22T08:16:40.267

Modified: 2026-09-22T19:07:00.983

Link: CVE-2026-74766

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-29T13:21:26Z

Weaknesses