CVE-2026-87080: Net::IDN::Punycode::PP versions before 2.590 for Perl decode a truncated label to a name containing a character it never encoded in decode_punycode

CVE-2026-87080 is a logic flaw in the pure-Perl Punycode decoder (Net::IDN::Punycode::PP) that processes truncated IDN labels incorrectly, reading past the end of the input string and deriving an extra character. This leads to a deterministic but incorrect decoding result. An attacker can craft a malicious IDN label that resolves successfully on systems using the vulnerable Perl backend but is rejected by systems using the XS backend, potentially causing inconsistencies in security-critical name resolution. The flaw is in the 'PP' backend, which is used when the XS backend fails to compile. As of the report, there is no known public exploit or exploitation in the wild.

Update Net::IDN::Punycode::PP to version 2.590 or later. Check your system's Perl modules for the installed version. Systems using the XS backend are not vulnerable.