Net::IDN::Punycode::PP versions before 2.590 for Perl decode a truncated label to a name containing a character it never encoded in decode_punycode

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-87080
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::PP versions before 2.590 for Perl decode a truncated label to a name containing a character it never encoded in decode_punycode. The pure-Perl decoder reads one digit at a time with four-argument substr and tests the result with defined to detect the end of the input. substr on an exhausted string returns the empty string rather than undef, so decoding continues past the end. The empty string converts to a digit value below the range, reducing the accumulator, and the decoder derives one extra code point and its position from it. The result is deterministic. The XS backend rejects the same label. Net::IDN::Punycode uses this backend wherever the XS does not build. The two backends disagree about what such a label means, so a sender can pick a label that one installation resolves to a name and another rejects.

Risk And Classification

Primary CVSS: v3.1 9.1 CRITICAL from ADP

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

EPSS: 0.003720000 probability, percentile 0.310880000 (date 2026-09-23)

Problem Types: CWE-1286 | CWE-1286 CWE-1286 Improper Validation of Syntactic Correctness of Input

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED9.1CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary9.1CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

CVSS v3.1 Breakdown

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

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

References

ReferenceSourceLinkTags
www.openwall.com/lists/oss-security/2026/09/22/15 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/48436c7ad2c4d4c6398110e11133754f... 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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