GHSA-4V8J-337R-265V
Vulnerability from github – Published: 2026-09-22 09:31 – Updated: 2026-09-22 18:33Net::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.
{
"affected": [],
"aliases": [
"CVE-2026-87082"
],
"database_specific": {
"cwe_ids": [
"CWE-835"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-22T08:16:40Z",
"severity": "HIGH"
},
"details": "Net::IDN::Punycode versions before 2.590 for Perl hang, crash or return a wrong label via unvalidated malformed UTF-8 in encode_punycode.\n\nNeither 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.\n\nThe 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.\n\nA direct caller encoding attacker-supplied bytes hangs, crashes or gets a label for a name the input never held.",
"id": "GHSA-4v8j-337r-265v",
"modified": "2026-09-22T18:33:28Z",
"published": "2026-09-22T09:31:13Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-87082"
},
{
"type": "WEB",
"url": "https://github.com/robrwo/Net-IDN-Encode/commit/0918fb4a951ed5f4494c4cf202419c2842507ea4.patch"
},
{
"type": "WEB",
"url": "https://github.com/robrwo/Net-IDN-Encode/commit/572af0183b3a6294e22c6b509268da09697cf77d.patch"
},
{
"type": "WEB",
"url": "https://github.com/robrwo/Net-IDN-Encode/commit/59dc7f2c605a897bcbfe0ac5eb2b8dbe6792348d.patch"
},
{
"type": "WEB",
"url": "https://github.com/robrwo/Net-IDN-Encode/commit/accb6df57ad107ec0c4bfb27b21551eed97c700e.patch"
},
{
"type": "WEB",
"url": "https://metacpan.org/release/PJCJ/Net-IDN-Encode-2.590-TRIAL/changes"
},
{
"type": "WEB",
"url": "http://www.openwall.com/lists/oss-security/2026/09/22/17"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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