{"id":"DEBIAN-CVE-2026-39821","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\".","modified":"2026-10-01T03:03:11.314741261Z","published":"2026-05-22T16:16:20.410Z","upstream":["CVE-2026-39821"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-39821"}],"affected":[{"package":{"name":"golang-golang-x-net","ecosystem":"Debian:12","purl":"pkg:deb/debian/golang-golang-x-net?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:0.10.0-1","1:0.11.0-1","1:0.14.0-1","1:0.15.0-1","1:0.15.0-2","1:0.17.0+dfsg-1","1:0.19.0+dfsg-1","1:0.20.0+dfsg-1","1:0.21.0+dfsg-1","1:0.22.0+dfsg-1","1:0.23.0+dfsg-1","1:0.24.0+dfsg-1","1:0.25.0+dfsg-1","1:0.26.0+dfsg-1","1:0.26.0+dfsg-2","1:0.27.0-1","1:0.27.0-2","1:0.47.0-1","1:0.47.0-2","1:0.53.0-1","1:0.53.0-2","1:0.53.0-2~bpo13+1","1:0.55.0-1","1:0.56.0-1","1:0.57.0-1","1:0.58.0-1","1:0.7.0+dfsg-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-39821.json"}},{"package":{"name":"golang-golang-x-net","ecosystem":"Debian:13","purl":"pkg:deb/debian/golang-golang-x-net?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:0.27.0-2","1:0.47.0-1","1:0.47.0-2","1:0.53.0-1","1:0.53.0-2","1:0.53.0-2~bpo13+1","1:0.55.0-1","1:0.56.0-1","1:0.57.0-1","1:0.58.0-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-39821.json"}},{"package":{"name":"golang-golang-x-net","ecosystem":"Debian:14","purl":"pkg:deb/debian/golang-golang-x-net?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:0.55.0-1"}]}],"versions":["1:0.27.0-2","1:0.47.0-1","1:0.47.0-2","1:0.53.0-1","1:0.53.0-2","1:0.53.0-2~bpo13+1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-39821.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N"}]}