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
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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 07:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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: 2026-09-22T07:25:37.650Z
Reserved: 2026-09-08T19:22:20.005Z
Link: CVE-2026-87082
Vulnrichment
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NVD
Status : Received
Published: 2026-09-22T08:16:40.973
Modified: 2026-09-22T08:16:40.973
Link: CVE-2026-87082
Redhat
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OpenCVE Enrichment
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