{"id":"CVE-2026-39821","summary":"Invoking failure to reject ASCII-only Punycode-encoded labels in golang.org/x/net/idna","details":"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\".","aliases":["GO-2026-5026"],"modified":"2026-06-10T18:29:08.543041577Z","published":"2026-05-22T15:01:21.462Z","related":["CGA-frmm-xgw5-xmhr","SUSE-SU-2026:2285-1","openSUSE-SU-2026:10856-1","openSUSE-SU-2026:10871-1","openSUSE-SU-2026:10872-1","openSUSE-SU-2026:10873-1","openSUSE-SU-2026:10875-1","openSUSE-SU-2026:10876-1","openSUSE-SU-2026:10877-1","openSUSE-SU-2026:10886-1","openSUSE-SU-2026:10887-1","openSUSE-SU-2026:10889-1","openSUSE-SU-2026:10899-1","openSUSE-SU-2026:10901-1","openSUSE-SU-2026:10908-1","openSUSE-SU-2026:10913-1","openSUSE-SU-2026:10921-1","openSUSE-SU-2026:10930-1","openSUSE-SU-2026:10971-1","openSUSE-SU-2026:10981-1","openSUSE-SU-2026:20853-1","openSUSE-SU-2026:20854-1","openSUSE-SU-2026:20888-1","openSUSE-SU-2026:20892-1","openSUSE-SU-2026:20893-1","openSUSE-SU-2026:20902-1"],"database_specific":{"cna_assigner":"Go","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39821.json","unresolved_ranges":[{"source":"AFFECTED_FIELD","extracted_events":[{"fixed":"0.55.0"}]}]},"references":[{"type":"WEB","url":"https://go.dev/cl/767220"},{"type":"WEB","url":"https://go.dev/issue/78760"},{"type":"WEB","url":"https://groups.google.com/g/golang-announce/c/iI-mYSI0lu8"},{"type":"WEB","url":"https://pkg.go.dev"},{"type":"WEB","url":"https://pkg.go.dev/vuln/GO-2026-5026"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39821.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-39821"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/golang/net","events":[{"introduced":"0"},{"fixed":"7770ec48d03fec35e378665337b4faca93c38423"}],"database_specific":{"source":"CPE_RANGE","cpe":"cpe:2.3:a:golang:net:*:*:*:*:*:go:*:*","extracted_events":[{"introduced":"0"},{"fixed":"0.55.0"}]}}],"versions":["v0.54.0","v0.41.0","v0.53.0","v0.52.0","v0.51.0","v0.50.0","v0.49.0","v0.48.0","v0.47.0","v0.46.0","v0.45.0","v0.44.0","v0.43.0","v0.42.0","v0.40.0","v0.39.0","v0.38.0","v0.37.0","v0.36.0","v0.35.0","v0.34.0","v0.33.0","v0.32.0","v0.31.0","v0.30.0","v0.29.0","v0.28.0","v0.27.0","v0.26.0","v0.25.0","v0.24.0","v0.23.0","v0.19.0","v0.22.0","v0.21.0","v0.20.0","v0.18.0","v0.17.0","v0.16.0","v0.15.0","v0.14.0","v0.13.0","v0.12.0","v0.11.0","v0.10.0","v0.9.0","v0.8.0","v0.7.0","v0.4.0","v0.6.0","v0.5.0","v0.3.0","v0.2.0","v0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-39821.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N"}]}