UBUNTU-CVE-2026-39821
- Source
- https://ubuntu.com/security/CVE-2026-39821
- Import Source
- https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-39821.json
- JSON Data
- https://api.test.osv.dev/v1/vulns/UBUNTU-CVE-2026-39821
- Upstream
- Downstream
- Related
- Published
- 2026-05-22T16:16:00Z
- Modified
- 2026-06-10T01:15:07.561274782Z
- Severity
-
- 9.6 (Critical) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N CVSS Calculator
- Ubuntu - medium
- Summary
- [none]
- 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".
- References
-
- https://ubuntu.com/security/CVE-2026-39821
- https://www.cve.org/CVERecord?id=CVE-2026-39821
- https://groups.google.com/g/golang-announce/c/iI-mYSI0lu8
- https://github.com/golang/go/issues/78760
- https://go.dev/cl/767220
- https://go.dev/issue/78760
- https://pkg.go.dev/vuln/GO-2026-5026
- https://ubuntu.com/security/notices/USN-8416-1
Affected packages
Ubuntu:Pro:18.04:LTS / golang-golang-x-net-dev
Package
- Name
- golang-golang-x-net-dev
- Purl
- pkg:deb/ubuntu/golang-golang-x-net-dev?arch=source&distro=esm-apps%2Fbionic
Affected ranges
- Type
- ECOSYSTEM
- Events
-
Introduced0Unknown introduced version / All previous versions are affectedFixed1:0.0+git20170629.c81e7f2+dfsg-2ubuntu0.1~esm3
Affected versions
1:0.*
1:0.0+git20170629.c81e7f2+dfsg-1ubuntu1
1:0.0+git20170629.c81e7f2+dfsg-1ubuntu2
1:0.0+git20170629.c81e7f2+dfsg-2
1:0.0+git20170629.c81e7f2+dfsg-2ubuntu0.1~esm1
1:0.0+git20170629.c81e7f2+dfsg-2ubuntu0.1~esm2
Ecosystem specific
{
"availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
"binaries": [
{
"binary_version": "1:0.0+git20170629.c81e7f2+dfsg-2ubuntu0.1~esm3",
"binary_name": "golang-go.net-dev"
},
{
"binary_name": "golang-golang-x-net-dev",
"binary_version": "1:0.0+git20170629.c81e7f2+dfsg-2ubuntu0.1~esm3"
}
]
}
Ubuntu:Pro:20.04:LTS / golang-golang-x-net-dev
Package
- Name
- golang-golang-x-net-dev
- Purl
- pkg:deb/ubuntu/golang-golang-x-net-dev?arch=source&distro=esm-apps%2Ffocal
Affected ranges
- Type
- ECOSYSTEM
- Events
-
Introduced0Unknown introduced version / All previous versions are affectedFixed1:0.0+git20190811.74dc4d7+dfsg-1ubuntu0.1~esm3
Affected versions
1:0.*
1:0.0+git20190811.74dc4d7+dfsg-1
1:0.0+git20190811.74dc4d7+dfsg-1ubuntu0.1~esm1
1:0.0+git20190811.74dc4d7+dfsg-1ubuntu0.1~esm2
Ecosystem specific
{
"availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
"binaries": [
{
"binary_name": "golang-go.net-dev",
"binary_version": "1:0.0+git20190811.74dc4d7+dfsg-1ubuntu0.1~esm3"
},
{
"binary_name": "golang-golang-x-net-dev",
"binary_version": "1:0.0+git20190811.74dc4d7+dfsg-1ubuntu0.1~esm3"
}
]
}