Neither backend checks that its input is well-formed UTF-8, so a string with the UTF-8 flag set over malformed bytes, as the :utf8 PerlIO layer produces from any malformed input, reaches the encoder unchecked. On perl 5.32 and later the XS backend reports a malformed sequence with a length of `(STRLEN)-1`, so the scan steps back one byte instead of forward and never ends. On earlier perls the XS returns a valid label for a different name. The pure-Perl backend runs a regex over the flagged string. Depending on the bytes, it aborts with SIGBUS on perl 5.28 and later, dies with a panic, or returns a wrong label.
The documented conversion functions match the label against Unicode properties first and that match dies on such a string, so only a direct call to encode_punycode reaches the defect. The decoder is not affected.
A direct caller encoding attacker-supplied bytes hangs, crashes or gets a label for a name the input never held.
Analysis
Analysis and contextual insights are available on OpenCVE Cloud.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
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Vendor Solution
Upgrade to Net-IDN-Encode 2.590-TRIAL or later.
Tracking
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Tue, 22 Sep 2026 18:30:00 +0000
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Tue, 22 Sep 2026 16:30:00 +0000
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Tue, 22 Sep 2026 07:30:00 +0000
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| Description | Net::IDN::Punycode versions before 2.590 for Perl hang, crash or return a wrong label via unvalidated malformed UTF-8 in encode_punycode. Neither backend checks that its input is well-formed UTF-8, so a string with the UTF-8 flag set over malformed bytes, as the :utf8 PerlIO layer produces from any malformed input, reaches the encoder unchecked. On perl 5.32 and later the XS backend reports a malformed sequence with a length of `(STRLEN)-1`, so the scan steps back one byte instead of forward and never ends. On earlier perls the XS returns a valid label for a different name. The pure-Perl backend runs a regex over the flagged string. Depending on the bytes, it aborts with SIGBUS on perl 5.28 and later, dies with a panic, or returns a wrong label. The documented conversion functions match the label against Unicode properties first and that match dies on such a string, so only a direct call to encode_punycode reaches the defect. The decoder is not affected. A direct caller encoding attacker-supplied bytes hangs, crashes or gets a label for a name the input never held. | |
| Title | Net::IDN::Punycode versions before 2.590 for Perl hang, crash or return a wrong label via unvalidated malformed UTF-8 in encode_punycode | |
| Weaknesses | CWE-1286 CWE-835 |
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Subscriptions
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MITRE
Status: PUBLISHED
Assigner: CPANSec
Published:
Updated: 2026-09-22T17:07:32.600Z
Reserved: 2026-09-08T19:22:20.005Z
Link: CVE-2026-87082
Vulnrichment
Updated: 2026-09-22T17:07:32.600Z
NVD
Status : Deferred
Published: 2026-09-22T08:16:40.973
Modified: 2026-09-22T19:07:00.983
Link: CVE-2026-87082
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-09-22T18:00:17Z