Net::IDN::Punycode up to 2.589 XS backend/pure-Perl backend decode_punycode resource consumption

Summaryinfo

A vulnerability was found in Net::IDN::Punycode up to 2.589. It has been classified as problematic. This issue affects the function decode_punycode of the component XS backend/pure-Perl backend. Performing a manipulation results in resource consumption. This vulnerability is reported as CVE-2026-87079. The attack is possible to be carried out remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as problematic has been found in Net::IDN::Punycode up to 2.589. This affects the function decode_punycode of the component XS backend/pure-Perl backend. The manipulation with an unknown input leads to a resource consumption vulnerability. CWE is classifying the issue as CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. This is going to have an impact on availability. The summary by CVE is:

Net::IDN::Punycode versions before 2.590 for Perl allow CPU exhaustion via quadratic insertion cost when decoding a long label in decode_punycode. The XS backend inserts each decoded code point into a UTF-8 buffer and finds the insertion point by scanning that buffer from the start, one character at a time. The scan runs once per code point over the output built so far, so the cost is quadratic in the label length. The pure-Perl backend downgrades its input to bytes so that substr can index it directly, but takes its working copy before the downgrade, so when the input carries the UTF-8 flag every substr on the copy scans from the start, with the same quadratic cost. Nothing bounds the label length in the to-Unicode direction. The 63-byte DNS limit is checked only when converting to ASCII, so domain_to_unicode and uts46_to_unicode pass an attacker-supplied label of any length to the decoder.

The advisory is shared at metacpan.org. This vulnerability is uniquely identified as CVE-2026-87079 since 09/08/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1499 for this issue.

Upgrading to version 2.590 eliminates this vulnerability.

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Productinfo

Name

• Net::IDN::Punycode

Version

• 2.589

CPE 2.3info

• 🔒

CPE 2.2info

• 🔒

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