Net::IDN::Punycode versions before 2.590 for Perl allow CPU exhaustion via quadratic insertion cost when decoding a long label in decode_punycode

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-87079
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 before 2.590 for Perl allow CPU exhaustion via quadratic insertion cost when decoding a long label in decode_punycode. The XS backend inserts each decoded code point into a UTF-8 buffer and finds the insertion point by scanning that buffer from the start, one character at a time. The scan runs once per code point over the output built so far, so the cost is quadratic in the label length. The pure-Perl backend downgrades its input to bytes so that substr can index it directly, but takes its working copy before the downgrade, so when the input carries the UTF-8 flag every substr on the copy scans from the start, with the same quadratic cost. Nothing bounds the label length in the to-Unicode direction. The 63-byte DNS limit is checked only when converting to ASCII, so domain_to_unicode and uts46_to_unicode pass an attacker-supplied label of any length to the decoder.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from ADP

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

EPSS: 0.003500000 probability, percentile 0.287580000 (date 2026-09-23)

Problem Types: CWE-407 | CWE-407 CWE-407 Inefficient Algorithmic Complexity

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

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

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

References

ReferenceSourceLinkTags
github.com/robrwo/Net-IDN-Encode/commit/00d723423b66810af26b88c552bedc61... 9b29abf9-4ab0-4765-b253-1875cd9b441e github.com
www.openwall.com/lists/oss-security/2026/09/22/14 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com
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/447c6b38ef5d4570329fa4f78690f4e1... 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

Solutions

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

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