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.
Analysis
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Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
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Vendor Solution
Upgrade to Net-IDN-Encode 2.590-TRIAL or later.
Tracking
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Tue, 22 Sep 2026 07:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | 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 | |
| Weaknesses | CWE-416 | |
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Subscriptions
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MITRE
Status: PUBLISHED
Assigner: CPANSec
Published:
Updated: 2026-09-22T07:19:09.359Z
Reserved: 2026-08-15T21:52:57.406Z
Link: CVE-2026-74766
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-22T08:16:40.267
Modified: 2026-09-22T08:16:40.267
Link: CVE-2026-74766
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-09-22T08:30:17Z