{"id":"CVE-2026-39821","revision":"dc83e3e751584a25b1a62cd70aa9bfe6","records":[{"revision":"dc83e3e751584a25b1a62cd70aa9bfe6","observedAt":"2026-10-25T09:17:18.747+00:00","statement":{"source":"nvd","id":"CVE-2026-39821","aliases":[],"title":"The ToASCII and ToUnicode functions incorrectly accept Punycode-encoded labels that decode to an ASCII-only label. For example, ToUnicode(\"xn--example-.com\") incorrectly returns the name \"example.com\" rather than an error. This behavior can…","description":"The ToASCII and ToUnicode functions incorrectly accept Punycode-encoded labels that decode to an ASCII-only label. For example, ToUnicode(\"xn--example-.com\") incorrectly returns the name \"example.com\" rather than an error. This behavior can lead to privilege escalation in programs using the idna package. For example, a program which performs privilege checks on the ASCII hostname may reject \"example.com\" but permit \"xn--example-.com\". If that program subsequently converts the ASCII hostname to Unicode, it will inadvertently permits access to the Unicode name \"example.com\".","state":0,"publishedAt":"2026-05-22T16:16:20.41+00:00","modifiedAt":"2026-09-17T12:18:05.767+00:00","affected":[],"metrics":[{"system":"CVSS 3.1 · 134c704f-9b21-4f2e-91b3-4a467353bcc0 · Secondary","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N","score":9.6,"severity":"CRITICAL"},{"system":"CVSS 3.1 · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c · Secondary","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N","score":8.2,"severity":"HIGH"}],"references":["https://go.dev/cl/767220","https://go.dev/issue/78760","https://groups.google.com/g/golang-announce/c/94pEornpRlI","https://groups.google.com/g/golang-announce/c/iI-mYSI0lu8","https://pkg.go.dev/vuln/GO-2026-5026","https://access.redhat.com/errata/RHSA-2026:23262","https://access.redhat.com/errata/RHSA-2026:23264","https://access.redhat.com/errata/RHSA-2026:26546","https://access.redhat.com/errata/RHSA-2026:26547","https://access.redhat.com/errata/RHSA-2026:30650","https://access.redhat.com/errata/RHSA-2026:30651","https://access.redhat.com/errata/RHSA-2026:30853","https://access.redhat.com/errata/RHSA-2026:30854","https://access.redhat.com/errata/RHSA-2026:30855","https://access.redhat.com/errata/RHSA-2026:33155","https://access.redhat.com/errata/RHSA-2026:33160","https://access.redhat.com/errata/RHSA-2026:33163","https://access.redhat.com/errata/RHSA-2026:33173","https://access.redhat.com/errata/RHSA-2026:33183","https://access.redhat.com/errata/RHSA-2026:33524","https://access.redhat.com/errata/RHSA-2026:33531","https://access.redhat.com/errata/RHSA-2026:34342","https://access.redhat.com/errata/RHSA-2026:34357","https://access.redhat.com/errata/RHSA-2026:34359","https://access.redhat.com/errata/RHSA-2026:34364","https://access.redhat.com/errata/RHSA-2026:34789","https://access.redhat.com/errata/RHSA-2026:35826","https://access.redhat.com/errata/RHSA-2026:35827","https://access.redhat.com/errata/RHSA-2026:35828","https://access.redhat.com/errata/RHSA-2026:35829","https://access.redhat.com/errata/RHSA-2026:35830","https://access.redhat.com/errata/RHSA-2026:35831","https://access.redhat.com/errata/RHSA-2026:35993","https://access.redhat.com/errata/RHSA-2026:35994","https://access.redhat.com/errata/RHSA-2026:36105","https://access.redhat.com/errata/RHSA-2026:36167","https://access.redhat.com/errata/RHSA-2026:36207","https://access.redhat.com/errata/RHSA-2026:36648","https://access.redhat.com/errata/RHSA-2026:36651","https://access.redhat.com/errata/RHSA-2026:36796","https://access.redhat.com/errata/RHSA-2026:36797","https://access.redhat.com/errata/RHSA-2026:36808","https://access.redhat.com/errata/RHSA-2026:36820","https://access.redhat.com/errata/RHSA-2026:36883","https://access.redhat.com/errata/RHSA-2026:37387","https://access.redhat.com/errata/RHSA-2026:37435","https://access.redhat.com/errata/RHSA-2026:37436","https://access.redhat.com/errata/RHSA-2026:38995","https://access.redhat.com/errata/RHSA-2026:39005","https://access.redhat.com/errata/RHSA-2026:39573","https://access.redhat.com/errata/RHSA-2026:39879","https://access.redhat.com/errata/RHSA-2026:40118","https://access.redhat.com/errata/RHSA-2026:40262","https://access.redhat.com/errata/RHSA-2026:40945","https://access.redhat.com/errata/RHSA-2026:41019","https://access.redhat.com/errata/RHSA-2026:41030","https://access.redhat.com/errata/RHSA-2026:41031","https://access.redhat.com/errata/RHSA-2026:41036","https://access.redhat.com/errata/RHSA-2026:41055","https://access.redhat.com/errata/RHSA-2026:41066","https://access.redhat.com/errata/RHSA-2026:41928","https://access.redhat.com/errata/RHSA-2026:41930","https://access.redhat.com/errata/RHSA-2026:42043","https://access.redhat.com/errata/RHSA-2026:42047","https://access.redhat.com/errata/RHSA-2026:42048","https://access.redhat.com/errata/RHSA-2026:42049","https://access.redhat.com/errata/RHSA-2026:42050","https://access.redhat.com/errata/RHSA-2026:42051","https://access.redhat.com/errata/RHSA-2026:42078","https://access.redhat.com/errata/RHSA-2026:42079","https://access.redhat.com/errata/RHSA-2026:42080","https://access.redhat.com/errata/RHSA-2026:42082","https://access.redhat.com/errata/RHSA-2026:42132","https://access.redhat.com/errata/RHSA-2026:42142","https://access.redhat.com/errata/RHSA-2026:42146","https://access.redhat.com/errata/RHSA-2026:42150","https://access.redhat.com/errata/RHSA-2026:42151","https://access.redhat.com/errata/RHSA-2026:42240","https://access.redhat.com/errata/RHSA-2026:42644","https://access.redhat.com/errata/RHSA-2026:42796","https://access.redhat.com/errata/RHSA-2026:42852","https://access.redhat.com/errata/RHSA-2026:43038","https://access.redhat.com/errata/RHSA-2026:43052","https://access.redhat.com/errata/RHSA-2026:43692","https://access.redhat.com/errata/RHSA-2026:44622","https://access.redhat.com/errata/RHSA-2026:44624","https://access.redhat.com/errata/RHSA-2026:46395","https://access.redhat.com/errata/RHSA-2026:47149","https://access.redhat.com/errata/RHSA-2026:47735","https://access.redhat.com/errata/RHSA-2026:47737","https://access.redhat.com/errata/RHSA-2026:47952","https://access.redhat.com/errata/RHSA-2026:49702","https://access.redhat.com/errata/RHSA-2026:49712","https://access.redhat.com/errata/RHSA-2026:50300","https://access.redhat.com/errata/RHSA-2026:50843","https://access.redhat.com/errata/RHSA-2026:51033","https://access.redhat.com/erra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NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Modified","weaknesses":["CWE-1289"],"productCriteria":["cpe:2.3:a:golang:net:*:*:*:*:*:go:*:*"],"sourceDates":{"published":"2026-05-22T16:16:20.410","lastModified":"2026-09-17T12:18:05.767"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-39821","identifiers":["CVE-2026-39821"]},"retained":false,"historicalAffected":[]}],"coverage":[]}