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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-74766
StatePUBLISHED
AssignerCPANSec
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-22 08:16:40 UTC
Updated2026-09-22 19:07:00 UTC
DescriptionNet::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.

Risk And Classification

Primary CVSS: v3.1 8.4 HIGH from ADP

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

EPSS: 0.001560000 probability, percentile 0.052060000 (date 2026-09-22)

Problem Types: CWE-416 | CWE-416 CWE-416 Use After Free

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED8.4HIGHCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary8.4HIGHCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

References

ReferenceSourceLinkTags
github.com/robrwo/Net-IDN-Encode/commit/259e74c5739175b063c5393a4ce4a070... 9b29abf9-4ab0-4765-b253-1875cd9b441e github.com
www.cve.org/CVERecord 9b29abf9-4ab0-4765-b253-1875cd9b441e www.cve.org
metacpan.org/release/PJCJ/Net-IDN-Encode-2.590-TRIAL/changes 9b29abf9-4ab0-4765-b253-1875cd9b441e metacpan.org
github.com/robrwo/Net-IDN-Encode/commit/2fbc71e4d8517ab65c5d5d35fda08637... 9b29abf9-4ab0-4765-b253-1875cd9b441e github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Additional Advisory Data

SourceTimeEvent
CNA2016-12-03T00:00:00.000ZVersion 2.301 released, introducing the defect.
CNA2026-09-17T00:00:00.000ZVersion 2.590-TRIAL released with fix.

Solutions

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

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