CVE-2026-39821
CVE-2026-39821 · Invoking failure to reject ASCII-only Punycode-encoded labels in golang.org/x/net/idna
This page contains facts from public vulnerability sources. Check the original advisory before updating.
This page shows selected source facts. See the linked advisories for the complete description and affected versions.
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".
CVSS 9.6 · Critical · EPSS 0.7% · Fix available
- Published
- Updated
Stack: system · containers
Affected products and versions
net/http
- Versions
- ≥ 0, < 1.25.13: Affected (semver)
- ≥ 1.26.0-0, < 1.26.6: Affected (semver)
- ≥ 1.27.0-0, < 1.27.0-rc.3: Affected (semver)
Update to 1.25.13; Update to 1.26.6
net/http/internal/http2
- Versions
- ≥ 0, < 1.25.13: Affected (semver)
- ≥ 1.26.0-0, < 1.26.6: Affected (semver)
- ≥ 1.27.0-0, < 1.27.0-rc.3: Affected (semver)
Update to 1.25.13; Update to 1.26.6
golang.org/x/net/idna
- Versions
- ≥ 0, < 0.55.0: Affected (semver)
Update to 0.55.0
golang-golang-x-net Debian:12
- 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
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
golang-golang-x-net Debian:13
- 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
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
golang-golang-x-net Debian:14
- 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
- Affected ranges
- ECOSYSTEM: < 1:0.55.0-1
Update to 1:0.55.0-1
golang-1.10 Ubuntu:14.04:LTS
- Versions
- 1.10.4-2ubuntu1~14.04.1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
golang-1.10 Ubuntu:16.04:LTS
- Versions
- 1.10.4-2ubuntu1~16.04.1
- 1.10.4-2ubuntu1~16.04.2
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
golang-1.6 Ubuntu:16.04:LTS
- Versions
- 1.6-0ubuntu1
- 1.6-0ubuntu2
- 1.6-0ubuntu3
- 1.6-0ubuntu4
- 1.6-0ubuntu5
- 1.6.1-0ubuntu1
- 1.6.2-0ubuntu5~16.04
- 1.6.2-0ubuntu5~16.04.2
- 1.6.2-0ubuntu5~16.04.3
- 1.6.2-0ubuntu5~16.04.4
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
juju-core Ubuntu:Pro:16.04:LTS
- Versions
- 1.24.6-0ubuntu3
- 1.25.0-0ubuntu1
- 1.25.0-0ubuntu2
- 1.25.0-0ubuntu3
- 2.0~beta4-0ubuntu2
- 2.0~beta6-0ubuntu1.16.04.1
- 2.0~beta7-0ubuntu1.16.04.1
- 2.0~beta12-0ubuntu1.16.04.1
- 2.0~beta15-0ubuntu2.16.04.1
- 2.0.0-0ubuntu0.16.04.2
- 2.0.2-0ubuntu0.16.04.1
- 2.0.2-0ubuntu0.16.04.2
- 2.3.1-0ubuntu0.16.04.1
- 2.3.2-0ubuntu0.16.04.1
- 2.3.7-0ubuntu0.16.04.1
- 2.3.7-0ubuntu0.16.04.1+esm1
- 2.3.7-0ubuntu0.16.04.1+esm2
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
lxd Ubuntu:Pro:16.04:LTS
- Versions
- 0.20-0ubuntu4
- 0.21-0ubuntu3
- 0.21-0ubuntu5
- 0.22-0ubuntu1
- 0.22-0ubuntu2
- 0.23-0ubuntu1
- 0.23-0ubuntu2
- 0.23-0ubuntu3
- 0.24-0ubuntu2
- 0.24-0ubuntu3
- 0.24-0ubuntu4
- 0.25-0ubuntu1
- 0.26-0ubuntu2
- 0.26-0ubuntu3
- 0.27-0ubuntu1
- 0.27-0ubuntu2
- 2.0.0~beta1-0ubuntu3
- 2.0.0~beta1-0ubuntu4
- 2.0.0~beta2-0ubuntu1
- 2.0.0~beta2-0ubuntu2
- 2.0.0~beta3-0ubuntu1
- 2.0.0~beta3-0ubuntu2
- 2.0.0~beta3-0ubuntu3
- 2.0.0~beta3-0ubuntu4
- 2.0.0~beta4-0ubuntu1
- 2.0.0~beta4-0ubuntu2
- 2.0.0~beta4-0ubuntu3
- 2.0.0~beta4-0ubuntu4
- 2.0.0~beta4-0ubuntu5
- 2.0.0~beta4-0ubuntu6
- 2.0.0~beta4-0ubuntu7
- 2.0.0~rc1-0ubuntu1
- 2.0.0~rc1-0ubuntu2
- 2.0.0~rc1-0ubuntu3
- 2.0.0~rc2-0ubuntu2
- 2.0.0~rc2-0ubuntu3
- 2.0.0~rc3-0ubuntu1
- 2.0.0~rc3-0ubuntu2
- 2.0.0~rc3-0ubuntu3
- 2.0.0~rc3-0ubuntu4
- 2.0.0~rc4-0ubuntu1
- 2.0.0~rc5-0ubuntu1
- 2.0.0~rc6-0ubuntu1
- 2.0.0~rc6-0ubuntu2
- 2.0.0~rc7-0ubuntu1
- 2.0.0~rc7-0ubuntu2
- 2.0.0~rc8-0ubuntu1
- 2.0.0~rc8-0ubuntu2
- 2.0.0~rc8-0ubuntu3
- 2.0.0~rc8-0ubuntu5
- 2.0.0~rc8-0ubuntu6
- 2.0.0~rc8-0ubuntu7
- 2.0.0~rc9-0ubuntu2
- 2.0.0~rc9-0ubuntu3
- 2.0.0~rc9-0ubuntu4
- 2.0.0~rc9-0ubuntu5
- 2.0.0-0ubuntu1
- 2.0.0-0ubuntu2
- 2.0.0-0ubuntu3
- 2.0.0-0ubuntu4
- 2.0.1-0ubuntu1~16.04.1
- 2.0.2-0ubuntu1~16.04.1
- 2.0.3-0ubuntu1~ubuntu16.04.2
- 2.0.4-0ubuntu1~ubuntu16.04.1
- 2.0.5-0ubuntu1~ubuntu16.04.1
- 2.0.8-0ubuntu1~ubuntu16.04.1
- 2.0.8-0ubuntu1~ubuntu16.04.2
- 2.0.9-0ubuntu1~16.04.1
- 2.0.9-0ubuntu1~16.04.2
- 2.0.10-0ubuntu1~16.04.1
- 2.0.10-0ubuntu1~16.04.2
- 2.0.11-0ubuntu1~16.04.2
- 2.0.11-0ubuntu1~16.04.4
- 2.0.11-0ubuntu1~16.04.4+esm1
- 2.0.11-0ubuntu1~16.04.4+esm2
- 2.0.11-0ubuntu1~16.04.4+esm3
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
containerd Ubuntu:Pro:16.04:LTS
- Versions
- 0.2.1-0ubuntu4~16.04
- 0.2.3-0ubuntu1~16.04
- 0.2.5-0ubuntu1~16.04.1
- 1.2.6-0ubuntu1~16.04.2
- 1.2.6-0ubuntu1~16.04.3
- 1.2.6-0ubuntu1~16.04.4
- 1.2.6-0ubuntu1~16.04.5
- 1.2.6-0ubuntu1~16.04.6
- 1.2.6-0ubuntu1~16.04.6+esm1
- 1.2.6-0ubuntu1~16.04.6+esm2
- 1.2.6-0ubuntu1~16.04.6+esm4
- 1.2.6-0ubuntu1~16.04.6+esm5
- 1.2.6-0ubuntu1~16.04.6+esm6
- 1.2.6-0ubuntu1~16.04.6+esm7
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
golang-1.13 Ubuntu:Pro:16.04:LTS
- Versions
- 1.13.8-1ubuntu1~16.04.2
- 1.13.8-1ubuntu1~16.04.3
- 1.13.8-1ubuntu1~16.04.3+esm2
- 1.13.8-1ubuntu1~16.04.3+esm3
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
golang-1.18 Ubuntu:Pro:16.04:LTS
- Versions
- 1.18.1-1ubuntu1~16.04.6
- 1.18.1-1ubuntu1~16.04.6+esm1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
google-guest-agent Ubuntu:Pro:16.04:LTS
- Versions
- 20201217.02-0ubuntu1~16.04.0
- 20230426.00-0ubuntu2~16.04.3
- 20231004.02-0ubuntu1~16.04.1
- 20231004.02-0ubuntu1~16.04.2
- 20240716.00-0ubuntu1~16.04.0
- 20240716.00-0ubuntu1~16.04.0+esm1
- 20240716.00-0ubuntu1~16.04.0+esm2
- 20240716.00-0ubuntu1~16.04.0+esm3
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
google-osconfig-agent Ubuntu:Pro:16.04:LTS
- Versions
- 20210219.00-0ubuntu1~16.04.0
- 20230504.00-0ubuntu1~16.04.0
- 20240320.00-0ubuntu1~16.04.0
- 20240524.03-0ubuntu2~16.04.0
- 20251028.00-0ubuntu2~16.04.1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
golang-1.10 Ubuntu:18.04:LTS
- Versions
- 1.10~rc1-1
- 1.10~rc1-1ubuntu1
- 1.10~rc1-2ubuntu1
- 1.10~rc2-1ubuntu1
- 1.10-1ubuntu1
- 1.10.1-1ubuntu2
- 1.10.4-2ubuntu1~18.04.1
- 1.10.4-2ubuntu1~18.04.2
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
lxd Ubuntu:Pro:18.04:LTS
- Versions
- 2.18-0ubuntu6
- 2.19-0ubuntu1
- 2.20-0ubuntu3
- 2.20-0ubuntu4
- 2.21-0ubuntu1
- 2.21-0ubuntu2
- 2.21-0ubuntu3
- 2.21-0ubuntu4
- 3.0.0~beta2-0ubuntu3
- 3.0.0~beta3-0ubuntu3
- 3.0.0~beta5-0ubuntu2
- 3.0.0~beta7-0ubuntu1
- 3.0.0-0ubuntu1
- 3.0.0-0ubuntu2
- 3.0.0-0ubuntu3
- 3.0.0-0ubuntu4
- 3.0.1-0ubuntu1~18.04.1
- 3.0.2-0ubuntu1~18.04.1
- 3.0.3-0ubuntu1~18.04.1
- 3.0.3-0ubuntu1~18.04.2
- 3.0.3-0ubuntu1~18.04.2+esm1
- 3.0.3-0ubuntu1~18.04.2+esm2
- 3.0.3-0ubuntu1~18.04.2+esm3
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
containerd Ubuntu:Pro:18.04:LTS
- Versions
- 0.2.5-0ubuntu2
- 1.2.6-0ubuntu1~18.04.1
- 1.2.6-0ubuntu1~18.04.2
- 1.3.3-0ubuntu1~18.04.1
- 1.3.3-0ubuntu1~18.04.2
- 1.3.3-0ubuntu1~18.04.3
- 1.3.3-0ubuntu1~18.04.4
- 1.4.4-0ubuntu1~18.04.2
- 1.5.2-0ubuntu1~18.04.1
- 1.5.2-0ubuntu1~18.04.2
- 1.5.2-0ubuntu1~18.04.3
- 1.5.5-0ubuntu3~18.04.1
- 1.5.5-0ubuntu3~18.04.2
- 1.5.9-0ubuntu1~18.04.1
- 1.5.9-0ubuntu1~18.04.2
- 1.6.12-0ubuntu1~18.04.1
- 1.6.12-0ubuntu1~18.04.1+esm1
- 1.6.12-0ubuntu1~18.04.1+esm2
- 1.6.12-0ubuntu1~18.04.1+esm3
- 1.6.12-0ubuntu1~18.04.1+esm4
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
golang-1.13 Ubuntu:Pro:18.04:LTS
- Versions
- 1.13.8-1ubuntu1~18.04.2
- 1.13.8-1ubuntu1~18.04.3
- 1.13.8-1ubuntu1~18.04.4
- 1.13.8-1ubuntu1~18.04.4+esm1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
golang-1.16 Ubuntu:Pro:18.04:LTS
- Versions
- 1.16.2-0ubuntu1~18.04.2
- 1.16.2-0ubuntu1~18.04.2+esm1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
golang-1.18 Ubuntu:Pro:18.04:LTS
- Versions
- 1.18.1-1ubuntu1~18.04.3
- 1.18.1-1ubuntu1~18.04.4
- 1.18.1-1ubuntu1~18.04.4+esm1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
golang-1.8 Ubuntu:18.04:LTS
- Versions
- 1.8.3-2ubuntu1
- 1.8.3-2ubuntu1.18.04.1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
golang-1.9 Ubuntu:18.04:LTS
- Versions
- 1.9.1-2ubuntu1
- 1.9.2-1ubuntu1
- 1.9.2-3ubuntu1
- 1.9.3-1ubuntu1
- 1.9.4-1ubuntu1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
Original sources
- 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
- https://access.redhat.com/security/cve/CVE-2026-39821
- https://bugzilla.redhat.com/show_bug.cgi?id=2480756
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39821.json
- https://access.redhat.com/errata/RHSA-2026:42079
- https://access.redhat.com/errata/RHSA-2026:42080
- https://access.redhat.com/errata/RHSA-2026:41019
- https://access.redhat.com/errata/RHSA-2026:66350
- https://access.redhat.com/errata/RHSA-2026:54191
- https://access.redhat.com/errata/RHSA-2026:42078
- https://access.redhat.com/errata/RHSA-2026:54757
- https://access.redhat.com/errata/RHSA-2026:54580
- https://access.redhat.com/errata/RHSA-2026:34789
- https://access.redhat.com/errata/RHSA-2026:42082
- https://access.redhat.com/errata/RHSA-2026:36796
- https://access.redhat.com/errata/RHSA-2026:57845
- https://access.redhat.com/errata/RHSA-2026:62549
- https://access.redhat.com/errata/RHSA-2026:65851
- https://access.redhat.com/errata/RHSA-2026:42150
- https://nvd.nist.gov/vuln/detail/CVE-2026-39821