CVE-2026-87082

Summary

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.

Affected Software

VendorProductVersion RangeStatus
0 < 2.590affected

Weaknesses

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

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: yes
    • Technical Impact: partial

CVE Program Container

Additional References

References