Punycode up to 2.589 XS backend decode_punycode allocation of resources

Summaryinfo

A vulnerability has been found in Punycode up to 2.589 and classified as problematic. This affects the function decode_punycode of the component XS backend. This manipulation causes allocation of resources. This vulnerability is registered as CVE-2026-87078. Remote exploitation of the attack is possible. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in Punycode up to 2.589. It has been declared as problematic. Affected by this vulnerability is the function decode_punycode of the component XS backend. The manipulation with an unknown input leads to a allocation of resources vulnerability. The CWE definition for the vulnerability is CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. As an impact it is known to affect availability. The summary by CVE is:

Net::IDN::Punycode versions from 2.302 before 2.590 for Perl leak the output buffer on every rejected label in decode_punycode. The XS backend allocates the scalar it returns before it validates the input, sizing the buffer at twice the input length. The scalar is released only on the success path, so each of the three croaks that reject a label leaves the scalar and its buffer allocated. Nothing bounds the label length in the to-Unicode direction, since the 63-byte DNS limit is checked only when converting to ASCII. Only the XS backend is affected. A sender who supplies invalid labels grows the process by twice the label length per rejected call, with no successful call needed.

It is possible to read the advisory at metacpan.org. This vulnerability is known as CVE-2026-87078 since 09/08/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 2.590 eliminates this vulnerability.

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Productinfo

Name

• Punycode

Version

• 2.589

CPE 2.3info

• 🔒

CPE 2.2info

• 🔒

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