CVE-2026-87082: Net::IDN::Punycode versions before 2.590 for Perl hang, crash or return a wrong label via unvalidated malformed UTF-8 in encode_punycode
Perl Net::IDN::Punycode before 2.590 can hang, crash, or mislabel malformed UTF-8.
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Vulnerability2 · 1 read
CVE-2026-87082
DoS and Data Corruption in Perl Net::IDN::Punycode via Malformed UTF-8
- CVSS 3.1
- 7.5 high
- EPSS
- —
- Published
- ·
- Modified
AI analysisSummaries by Vani AI
CVE-2026-87082 is a denial-of-service and data corruption vulnerability in the Net::IDN::Punycode Perl library. The flaw is triggered when the encode_punycode function processes malformed UTF-8 input passed through the :utf8 PerlIO layer, bypassing necessary validation checks. Depending on the Perl version and backend used, this can cause the library to hang indefinitely, crash with a panic or SIGBUS error, or return a Punycode label for a different domain name than the input. The decoder is not affected, and only direct calls to encode_punycode are vulnerable. As of now, there are no known public proofs-of-concept or reports of in-the-wild exploitation.
What to do: Upgrade Net::IDN::Punycode to version 2.590 or later. If you cannot upgrade, avoid passing strings with the :utf8 PerlIO layer that may contain malformed UTF-8 to the encode_punycode function. Ensure any user-supplied input is validated as well-formed UTF-8 before processing.
| Product | Affected |
|---|---|
| perl Net::IDN::Punycode | before 2.590 |
Estimated exposure
nicheNo basis for an estimate.
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description · NVD
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.
- Weakness
- CWE-835, CWE-1286
- Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H