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CVE-2026-87082                                       CPAN Security Group
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        CVE ID:  CVE-2026-87082

  Distribution:  Net-IDN-Encode
      Versions:  before 2.590
      MetaCPAN:  https://metacpan.org/dist/Net-IDN-Encode
      VCS Repo:  https://github.com/robrwo/Net-IDN-Encode

Net::IDN::Punycode versions before 2.590 for Perl hang, crash or return
a wrong label via unvalidated malformed UTF-8 in encode_punycode

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.

Problem types
-------------
- CWE-835 Loop with Unreachable Exit Condition ('Infinite Loop')
- CWE-1286 Improper Validation of Syntactic Correctness of Input

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

References
----------
https://metacpan.org/release/PJCJ/Net-IDN-Encode-2.590-TRIAL/changes
https://github.com/robrwo/Net-IDN-Encode/commit/0918fb4a951ed5f4494c4cf202419c2842507ea4.patch
https://github.com/robrwo/Net-IDN-Encode/commit/59dc7f2c605a897bcbfe0ac5eb2b8dbe6792348d.patch
https://github.com/robrwo/Net-IDN-Encode/commit/accb6df57ad107ec0c4bfb27b21551eed97c700e.patch
https://github.com/robrwo/Net-IDN-Encode/commit/572af0183b3a6294e22c6b509268da09697cf77d.patch

--
Paul Johnson - xxxxxx@pjcj.net