CVE-2026-87078

Net::IDN::Punycode versions from 2.302 before 2.590 for Perl leak the output buffer on every rejected label in decode_punycode

Published Sep 22, 2026 CVSS 3.1 · 9.1 Critical EPSS < 1% KEV · Not listed
Description
Net::IDN::Punycode versions from 2.302 before 2.590 for Perl leak the output buffer on every rejected label in decode_punycode.

The XS backend allocates the scalar it returns before it validates the input, sizing the buffer at twice the input length. The scalar is released only on the success path, so each of the three croaks that reject a label leaves the scalar and its buffer allocated. Nothing bounds the label length in the to-Unicode direction, since the 63-byte DNS limit is checked only when converting to ASCII.

Only the XS backend is affected.

A sender who supplies invalid labels grows the process by twice the label length per rejected call, with no successful call needed.

Remediation

Vendor Solution

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

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Perl
Perl net::idn::punycode
Vendors & Products Perl
Perl net::idn::punycode
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description Net::IDN::Punycode versions from 2.302 before 2.590 for Perl leak the output buffer on every rejected label in decode_punycode. The XS backend allocates the scalar it returns before it validates the input, sizing the buffer at twice the input length. The scalar is released only on the success path, so each of the three croaks that reject a label leaves the scalar and its buffer allocated. Nothing bounds the label length in the to-Unicode direction, since the 63-byte DNS limit is checked only when converting to ASCII. Only the XS backend is affected. A sender who supplies invalid labels grows the process by twice the label length per rejected call, with no successful call needed.
Title Net::IDN::Punycode versions from 2.302 before 2.590 for Perl leak the output buffer on every rejected label in decode_punycode
Weaknesses CWE-401
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
CPANSec
Published
Updated
Sep 22, 2026, 5:07 PM
Reserved
Sep 8, 2026, 7:22 PM
Status
Deferred
Published
Sep 22, 2026, 8:16 AM
Modified
Sep 22, 2026, 7:07 PM