CVE-2026-87082
Received
Received - Intake
Net::IDN::Punycode UTF-8 Handling DoS and Label Corruption
Vulnerability report for CVE-2026-87082, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-09-22
Last updated on: 2026-09-22
Assigner: CPANSec
Description
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.
CVSS Scores
EPSS Scores
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| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| robrwo | net_idn_punycode | to 2.590 (exc) |
| robrwo | net_idn_punycode | From 5.36 (inc) to 5.40.0 (inc) |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-835 | The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop. |
| CWE-1286 | The product receives input that is expected to be well-formed - i.e., to comply with a certain syntax - but it does not validate or incorrectly validates that the input complies with the syntax. |
