# CVE-2026-87082: libnet-idn-encode-perl: Net::IDN::Punycode versions before 2.590 for Perl hang, crash or return a wrong label via unvalidated malformed UTF-8...

CVE-2026-87082 is fixed in 4 products on 1 platform, first by DEBIAN-CVE-2026-87082, released September 22, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-87082
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0042
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 22, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libnet-idn-encode-perl Debian 14 | 2.600-1 | [DEBIAN-CVE-2026-87082](https://patchblox.com/security/data/fix/linux/debian-cve-2026-87082.md) | Sep 22, 2026 |
| Linux | perl-Net-IDN-Encode amzn 2023 | 2.590-1.amzn2023.0.1 | [ALAS2023-2026-3190](https://patchblox.com/security/data/fix/linux/alas2023-2026-3190.md) | Nov 7, 2026 |
| Linux | perl-Net-IDN-Encode-debuginfo amzn 2023 | 2.590-1.amzn2023.0.1 | [ALAS2023-2026-3190](https://patchblox.com/security/data/fix/linux/alas2023-2026-3190.md) | Nov 7, 2026 |
| Linux | perl-Net-IDN-Encode-debugsource amzn 2023 | 2.590-1.amzn2023.0.1 | [ALAS2023-2026-3190](https://patchblox.com/security/data/fix/linux/alas2023-2026-3190.md) | Nov 7, 2026 |

---

Data as of 2026-11-10T07:50:38Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data

Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.