PJCJ Net::IDN::Punycode up to 2.589 XS backend decode_punycode use after free

Summaryinfo

A vulnerability was found in PJCJ Net::IDN::Punycode up to 2.589 and classified as critical. This vulnerability affects the function decode_punycode of the component XS backend. Such manipulation leads to use after free. This vulnerability is documented as CVE-2026-74766. The attack can be executed remotely. There is not any exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in PJCJ Net::IDN::Punycode up to 2.589. It has been rated as critical. Affected by this issue is the function decode_punycode of the component XS backend. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is confidentiality, integrity, and availability. CVE summarizes:

Net::IDN::Punycode versions from 2.301 before 2.590 for Perl allow a heap use-after-free via a decoded code point that reallocates the output buffer in decode_punycode. The XS backend inserts each decoded code point into the string buffer of the scalar it returns. decode_punycode computes the insertion pointer first and only then grows the buffer when the code point does not fit. The growth reallocates the buffer and updates every pointer except the insertion pointer, so the move that follows and the write of the code point go through a freed pointer. The buffer starts at twice the label length, and a code point above U+FFFF takes four bytes in the output, so a label of such code points outgrows it and forces the reallocation. Version 2.301, the fix for CVE-2016-15059, introduced the defect. Only the XS backend is affected. Decoding an attacker-supplied punycode label reads and writes freed heap memory.

The advisory is shared for download at metacpan.org. This vulnerability is handled as CVE-2026-74766 since 08/15/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are known technical details, but no exploit is available.

Upgrading to version 2.590 eliminates this vulnerability.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Vendor

• PJCJ

Name

• Net::IDN::Punycode

Version

• 2.589

CPE 2.3info

• 🔒

CPE 2.2info

• 🔒

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