{"id":"CVE-2026-39821","revision":"6f5e9e3864014237b7966b4b6e3ded83","records":[{"revision":"6f5e9e3864014237b7966b4b6e3ded83","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-39821","aliases":[],"title":"Invoking failure to reject ASCII-only Punycode-encoded labels in golang.org/x/net/idna","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":"2026-05-22T15:01:21.462+00:00","modifiedAt":"2026-09-17T12:04:30.881+00:00","affected":[{"ecosystem":"https://pkg.go.dev","name":"net/http","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"Go standard library\",\n                    \"product\": \"net/http\",\n                    \"collectionURL\": \"https://pkg.go.dev\",\n                    \"packageName\": \"net/http\",\n                    \"versions\": [\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"1.25.13\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"1.26.0-0\",\n                            \"lessThan\": \"1.26.6\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"1.27.0-0\",\n                            \"lessThan\": \"1.27.0-rc.3\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        }\n                    ],\n                    \"programRoutines\": [\n                        {\n                            \"name\": \"idnaASCII\"\n                        },\n                        {\n                            \"name\": \"Client.CloseIdleConnections\"\n                        },\n                        {\n                            \"name\": \"Client.Do\"\n                        },\n                        {\n                            \"name\": \"Client.Get\"\n                        },\n                        {\n                            \"name\": \"Client.Head\"\n                        },\n                        {\n                            \"name\": \"Client.Post\"\n                        },\n                        {\n                            \"name\": \"Client.PostForm\"\n                        },\n                        {\n                            \"name\": \"ClientConn.Close\"\n                        },\n                        {\n                            \"name\": \"ClientConn.RoundTrip\"\n                        },\n                        {\n                            \"name\": \"Get\"\n                        },\n                        {\n                            \"name\": \"Head\"\n                        },\n                        {\n                            \"name\": \"Post\"\n                        },\n                        {\n                            \"name\": \"PostForm\"\n                        },\n                        {\n                            \"name\": \"Transport.CloseIdleConnections\"\n                        },\n                        {\n                            \"name\": \"Transport.NewClientConn\"\n                        },\n                        {\n                            \"name\": \"Transport.RoundTrip\"\n                        },\n                        {\n                            \"name\": \"http1ClientConn.Close\"\n                        },\n                        {\n                            \"name\": \"http1ClientConn.RoundTrip\"\n                        },\n                        {\n                            \"name\": \"http2ClientConn.RoundTrip\"\n                        },\n                        {\n                            \"name\": \"http2RoundTripper.RoundTrip\"\n                        }\n                    ],\n                    \"defaultStatus\": \"unaffected\"\n                }"},{"ecosystem":"https://pkg.go.dev","name":"net/http/internal/http2","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"Go standard library\",\n                    \"product\": \"net/http/internal/http2\",\n                    \"collectionURL\": \"https://pkg.go.dev\",\n                    \"packageName\": \"net/http/internal/http2\",\n                    \"versions\": [\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"1.25.13\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"1.26.0-0\",\n                            \"lessThan\": \"1.26.6\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"1.27.0-0\",\n                            \"lessThan\": \"1.27.0-rc.3\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        }\n                    ],\n                    \"programRoutines\": [\n                        {\n                            \"name\": \"authorityAddr\"\n                        },\n                        {\n                            \"name\": \"Transport.AddConn\"\n                        },\n                        {\n                            \"name\": \"Transport.RoundTrip\"\n                        },\n                        {\n                            \"name\": \"Transport.RoundTripOpt\"\n                        }\n                    ],\n                    \"defaultStatus\": \"unaffected\"\n                }"},{"ecosystem":"https://pkg.go.dev","name":"golang.org/x/net/idna","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"golang.org/x/net\",\n                    \"product\": \"golang.org/x/net/idna\",\n                    \"collectionURL\": \"https://pkg.go.dev\",\n                    \"packageName\": \"golang.org/x/net/idna\",\n                    \"versions\": [\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"0.55.0\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        }\n                    ],\n                    \"programRoutines\": [\n                        {\n                            \"name\": \"Profile.process\"\n                        },\n                        {\n                            \"name\": \"Profile.ToASCII\"\n                        },\n                        {\n                            \"name\": \"Profile.ToUnicode\"\n                        },\n                        {\n                            \"name\": \"ToASCII\"\n                        },\n                        {\n                            \"name\": \"ToUnicode\"\n                        }\n                    ],\n                    \"defaultStatus\": \"unaffected\"\n                }"}],"metrics":[],"references":["https://go.dev/cl/767220","https://go.dev/issue/78760","https://groups.google.com/g/golang-announce/c/iI-mYSI0lu8","https://groups.google.com/g/golang-announce/c/94pEornpRlI","https://pkg.go.dev/vuln/GO-2026-5026"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-39821","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-39821","identifiers":["CVE-2026-39821"]},"retained":false,"historicalAffected":[]}],"coverage":[]}