CVE-2026-39821
Vulnerability Summary
Timeline
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".
CVSS Metrics
- v3.1•CRITICAL•Score: 9.6CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N
- v3.1•HIGH•Score: 8.8CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:L
EPSS Trends
Current EPSS score: 0.69%• Percentile: 51%
Techniques & Countermeasures
- CWE-1289•Improper Validation of Unsafe Equivalence in Input
The product receives an input value that is used as a resource identifier or other type of reference, but it does not validate or incorrectly validates that the input is equivalent to a potentially-unsafe value.
Affected Systems
- chainguard•aactl
< 0.4.12-r68
- chainguard•actions-runner-controller
< 0.14.2-r3
- chainguard•actions-runner-controller-fips
< 0.14.2-r7
- chainguard•addon-resizer
< 1.8.23-r20
- chainguard•addon-resizer-fips
< 1.8.23-r19
- chainguard•age
< 0
- chainguard•age-fips
< 0
- chainguard•agentbeat
< 9.2.7-r13
- chainguard•agentbeat-fips
< 9.2.7-r21
- chainguard•amass
< 5.1.1-r7
- chainguard•amazon-cloudwatch-agent
< 1.300072.0-r1
- chainguard•amazon-cloudwatch-agent-amazon-cloudwatch-agent-config-wizard
< 0
- chainguard•amazon-cloudwatch-agent-amazon-cloudwatch-agent-config-wizard-fips
< 0
- chainguard•amazon-cloudwatch-agent-config-downloader
< 0
- chainguard•amazon-cloudwatch-agent-config-downloader-fips
< 0
- chainguard•amazon-cloudwatch-agent-config-translator
< 0
- chainguard•amazon-cloudwatch-agent-config-translator-fips
< 0
- chainguard•amazon-cloudwatch-agent-fips
< 1.300072.0-r1
- chainguard•amazon-cloudwatch-agent-operator
< 3.5.0-r0
- chainguard•amazon-cloudwatch-agent-operator-fips
< 3.4.2-r6
- chainguard•amazon-cloudwatch-agent-start-amazon-cloudwatch-agent
< 0
- chainguard•amazon-cloudwatch-agent-start-amazon-cloudwatch-agent-fips
< 0
- chainguard•amazon-ecs-agent
< 0
- chainguard•amazon-ecs-agent-fips
< 0
- chainguard•amazon-ecs-cni-plugins
< 2024.9.0_git20260617-r3 | < 0
- chainguard•amazon-ecs-cni-plugins-fips
< 2024.9.0_git20260617-r5 | < 0
- chainguard•amazon-eks-ami
< 0
- chainguard•amazon-eks-ami-fips
< 0
- chainguard•amazon-k8s-cni
< 0 | < 1.22.1-r2
- chainguard•amazon-k8s-cni-fips
< 0 | < 1.22.1-r2
- chainguard•amazon-k8s-cni-init-fips-compat
< 0
- chainguard•amazon-ssm-agent
< 0 | < 3.3.4851.0-r3
- chainguard•amazon-ssm-agent-ecs-exec
< 3.3.4851.0-r3
- chainguard•amazon-ssm-agent-ecs-exec-fips
< 3.3.4851.0-r3
- chainguard•amazon-ssm-agent-fips
< 0 | < 3.3.4851.0-r3
- chainguard•amazon-vpc-cni-plugins
< 0
- chainguard•ansible-operator
< 1.42.3-r10
- chainguard•ansible-operator-fips
< 1.42.3-r7
- chainguard•apache-beam-java-11-sdk
< 0
- chainguard•apache-beam-java-17-sdk
< 0
- chainguard•apache-beam-java-21-sdk
< 0
- chainguard•apache-beam-python-3.13-sdk
< 0
- chainguard•apache-beam-python-3.14-sdk
< 0
- chainguard•apache-exporter
< 0
- chainguard•apiserver-network-proxy-0.35
< 0.35.0-r4
- chainguard•apiserver-network-proxy-0.35-agent
< 0.35.0-r4
- chainguard•apiserver-network-proxy-0.36
< 0.36.0-r4
- chainguard•apiserver-network-proxy-0.36-agent
< 0.36.0-r4
- chainguard•apiserver-network-proxy-fips-0.34
< 0.34.0-r8
- chainguard•apiserver-network-proxy-fips-0.34-agent
< 0.34.0-r8
Showing first 50 affected entries in server-rendered view.
References (259)
- https://go.dev/cl/767220
- https://go.dev/issue/78760
- https://groups.google.com/g/golang-announce/c/iI-mYSI0lu8
- 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-2026:30855
- https://access.redhat.com/errata/RHSA-2026:30853
- https://access.redhat.com/errata/RHSA-2026:30854
- https://access.redhat.com/errata/RHSA-2026:30651
- https://access.redhat.com/errata/RHSA-2026:26547
- https://access.redhat.com/errata/RHSA-2026:26546
- https://access.redhat.com/errata/RHSA-2026:23262
- https://access.redhat.com/errata/RHSA-2026:23264
- https://access.redhat.com/errata/RHSA-2026:33155
- https://access.redhat.com/errata/RHSA-2026:33160
- https://access.redhat.com/errata/RHSA-2026:33163
- https://access.redhat.com/errata/RHSA-2026:33173
- https://access.redhat.com/errata/RHSA-2026:33183
- https://access.redhat.com/errata/RHSA-2026:30650
- https://access.redhat.com/errata/RHSA-2026:34789
- https://access.redhat.com/errata/RHSA-2026:35827
- https://access.redhat.com/errata/RHSA-2026:35826
- https://access.redhat.com/errata/RHSA-2026:34357
- https://access.redhat.com/errata/RHSA-2026:35830
- https://access.redhat.com/errata/RHSA-2026:35831
- https://access.redhat.com/errata/RHSA-2026:35828
- https://access.redhat.com/errata/RHSA-2026:35829
- https://access.redhat.com/errata/RHSA-2026:34359
- https://access.redhat.com/errata/RHSA-2026:34342
- https://access.redhat.com/errata/RHSA-2026:34364
- https://access.redhat.com/errata/RHSA-2026:36207
- https://access.redhat.com/errata/RHSA-2026:33531
- https://access.redhat.com/errata/RHSA-2026:33524
- https://access.redhat.com/errata/RHSA-2026:36648
- https://access.redhat.com/errata/RHSA-2026:35994
- https://access.redhat.com/errata/RHSA-2026:35993
- https://access.redhat.com/errata/RHSA-2026:36105
- https://access.redhat.com/errata/RHSA-2026:36167
- https://access.redhat.com/errata/RHSA-2026:36796
- https://access.redhat.com/errata/RHSA-2026:36808
- https://access.redhat.com/errata/RHSA-2026:36651
- https://access.redhat.com/errata/RHSA-2026:36820
- https://access.redhat.com/errata/RHSA-2026:36797
- https://access.redhat.com/errata/RHSA-2026:36883
- https://access.redhat.com/errata/RHSA-2026:37387
- https://access.redhat.com/errata/RHSA-2026:37436
- https://access.redhat.com/errata/RHSA-2026:37435
- https://access.redhat.com/errata/RHSA-2026:39005
- https://access.redhat.com/errata/RHSA-2026:38995
- https://access.redhat.com/errata/RHSA-2026:41019
- https://access.redhat.com/errata/RHSA-2026:39573
- https://access.redhat.com/errata/RHSA-2026:39879
- https://access.redhat.com/errata/RHSA-2026:41030
- https://access.redhat.com/errata/RHSA-2026:40945
- https://access.redhat.com/errata/RHSA-2026:40118
- https://access.redhat.com/errata/RHSA-2026:41036
- https://access.redhat.com/errata/RHSA-2026:41031
- https://access.redhat.com/errata/RHSA-2026:41066
- https://access.redhat.com/errata/RHSA-2026:40262
- https://access.redhat.com/errata/RHSA-2026:41055
- https://access.redhat.com/errata/RHSA-2026:40119
- https://access.redhat.com/errata/RHSA-2026:41930
- https://access.redhat.com/errata/RHSA-2026:42079
- https://access.redhat.com/errata/RHSA-2026:42080
- https://access.redhat.com/errata/RHSA-2026:42078
- https://access.redhat.com/errata/RHSA-2026:42082
- https://access.redhat.com/errata/RHSA-2026:42150
- https://access.redhat.com/errata/RHSA-2026:42151
- https://access.redhat.com/errata/RHSA-2026:42240
- https://access.redhat.com/errata/RHSA-2026:42132
- https://access.redhat.com/errata/RHSA-2026:42142
- https://access.redhat.com/errata/RHSA-2026:41928
- https://access.redhat.com/errata/RHSA-2026:42644
- https://access.redhat.com/errata/RHSA-2026:42146
- https://access.redhat.com/errata/RHSA-2026:42043
- https://access.redhat.com/errata/RHSA-2026:42047
- https://access.redhat.com/errata/RHSA-2026:42050
- https://access.redhat.com/errata/RHSA-2026:42051
- https://access.redhat.com/errata/RHSA-2026:42049
- https://access.redhat.com/errata/RHSA-2026:42048
- https://access.redhat.com/errata/RHSA-2026:42852
- https://access.redhat.com/errata/RHSA-2026:43038
- https://access.redhat.com/errata/RHSA-2026:42796
- https://access.redhat.com/errata/RHSA-2026:54191
- https://access.redhat.com/errata/RHSA-2026:53413
- https://access.redhat.com/errata/RHSA-2026:53374
- https://access.redhat.com/errata/RHSA-2026:51187
- https://access.redhat.com/errata/RHSA-2026:46395
- https://access.redhat.com/errata/RHSA-2026:53412
- https://access.redhat.com/errata/RHSA-2026:51112
- https://access.redhat.com/errata/RHSA-2026:52826
- https://access.redhat.com/errata/RHSA-2026:53415
- https://access.redhat.com/errata/RHSA-2026:50843
- https://access.redhat.com/errata/RHSA-2026:47952
- https://access.redhat.com/errata/RHSA-2026:47149
- https://access.redhat.com/errata/RHSA-2026:53530
- https://access.redhat.com/errata/RHSA-2026:51033
- https://access.redhat.com/errata/RHSA-2026:43692
- https://access.redhat.com/errata/RHSA-2026:47737
- https://access.redhat.com/errata/RHSA-2026:50300
- https://access.redhat.com/errata/RHSA-2026:54287
- https://access.redhat.com/errata/RHSA-2026:54285
- https://access.redhat.com/errata/RHSA-2026:54283
- https://access.redhat.com/errata/RHSA-2026:44624
- https://access.redhat.com/errata/RHSA-2026:43052
- https://access.redhat.com/errata/RHSA-2026:51341
- https://access.redhat.com/errata/RHSA-2026:51194
- https://access.redhat.com/errata/RHSA-2026:44622
- https://access.redhat.com/errata/RHSA-2026:47735
- https://access.redhat.com/errata/RHSA-2026:54401
- https://access.redhat.com/errata/RHSA-2026:54441
- https://access.redhat.com/errata/RHSA-2026:54284
- https://access.redhat.com/errata/RHSA-2026:54286
- https://access.redhat.com/errata/RHSA-2026:54274
- https://access.redhat.com/errata/RHSA-2026:54395
- https://access.redhat.com/errata/RHSA-2026:54435
- https://www.suse.com/support/update/announcement/2026/suse-su-202622848-1/
- https://bugzilla.suse.com/1266604
- https://www.suse.com/security/cve/CVE-2026-39821
- https://www.suse.com/support/update/announcement/2026/suse-su-20263197-1/
- https://bugzilla.suse.com/1266477
- https://bugzilla.suse.com/1266482
- https://bugzilla.suse.com/1266541
- https://bugzilla.suse.com/1266547
- https://www.suse.com/support/update/announcement/2026/suse-su-20263198-1/
- https://www.suse.com/support/update/announcement/2026/suse-su-20263209-1/
- https://bugzilla.suse.com/1266603
- https://www.suse.com/support/update/announcement/2026/suse-su-20263210-1/
- https://www.suse.com/support/update/announcement/2026/suse-su-20263416-1/
- https://bugzilla.suse.com/1266552
- https://www.suse.com/support/update/announcement/2026/suse-su-20263421-1/
- https://www.suse.com/support/update/announcement/2026/suse-su-20263471-1/
- https://www.suse.com/support/update/announcement/2026/suse-su-20263472-1/
- https://www.suse.com/support/update/announcement/2026/suse-su-20263473-1/
- https://bugzilla.suse.com/1266651
- https://access.redhat.com/security/updates/classification/#important
- https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_30853.json
- https://www.cve.org/CVERecord?id=CVE-2026-39821
- https://nvd.nist.gov/vuln/detail/CVE-2026-39821
- https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_30854.json
- https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_30855.json
- https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_34789.json
- https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_35826.json
- https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_35829.json
- https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_35830.json
- https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_35831.json
- https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_52826.json
- https://security-tracker.debian.org/tracker/CVE-2026-39821
- https://bugzilla.suse.com/1266618
- https://bugzilla.suse.com/1266602
- https://bugzilla.suse.com/1266617
- https://groups.google.com/g/golang-announce/c/94pEornpRlI
- https://access.redhat.com/errata/RHSA-2026:54757
- https://access.redhat.com/errata/RHSA-2026:54531
- https://access.redhat.com/errata/RHSA-2026:54580
- https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_54580.json
- https://access.redhat.com/errata/RHSA-2026:56143
- https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_56143.json
- https://access.redhat.com/errata/RHSA-2026:56223
- https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_56223.json
- https://access.redhat.com/errata/RHSA-2026:56340
- https://access.redhat.com/errata/RHSA-2026:56431
- https://access.redhat.com/errata/RHSA-2026:57194
- https://access.redhat.com/errata/RHSA-2026:57541
- https://www.suse.com/support/update/announcement/-2026-3712/suse-ru-20263712-1/
- https://bugzilla.suse.com/1243168
- https://bugzilla.suse.com/1244141
- https://bugzilla.suse.com/1245944
- https://bugzilla.suse.com/1247004
- https://bugzilla.suse.com/1253505
- https://bugzilla.suse.com/1254201
- https://bugzilla.suse.com/1257102
- https://bugzilla.suse.com/1257295
- https://bugzilla.suse.com/1258500
- https://bugzilla.suse.com/1258567
- https://bugzilla.suse.com/1259225
- https://bugzilla.suse.com/1259254
- https://bugzilla.suse.com/1259594
- https://bugzilla.suse.com/1259720
- https://bugzilla.suse.com/1260342
- https://bugzilla.suse.com/1260396
- https://bugzilla.suse.com/1261195
- https://bugzilla.suse.com/1262012
- https://bugzilla.suse.com/1262168
- https://bugzilla.suse.com/1262664
- https://bugzilla.suse.com/1263822
- https://bugzilla.suse.com/1263823
- https://bugzilla.suse.com/1265334
- https://bugzilla.suse.com/1266481
- https://bugzilla.suse.com/1267619
- https://bugzilla.suse.com/1267871
- https://bugzilla.suse.com/1268006
- https://bugzilla.suse.com/1268151
- https://bugzilla.suse.com/1268229
- https://bugzilla.suse.com/1268309
- https://bugzilla.suse.com/1268325
- https://bugzilla.suse.com/1268567
- https://bugzilla.suse.com/1268570
- https://bugzilla.suse.com/1268673
- https://bugzilla.suse.com/1269192
- https://bugzilla.suse.com/1269267
- https://bugzilla.suse.com/1269408
- https://bugzilla.suse.com/1270040
- https://bugzilla.suse.com/1274571
- https://bugzilla.suse.com/1274984
- https://bugzilla.suse.com/1275217
- https://access.redhat.com/errata/RHSA-2026:59549
- https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_59549.json
- https://access.redhat.com/errata/RHSA-2026:57845
- https://access.redhat.com/errata/RHSA-2026:49702
- https://access.redhat.com/errata/RHSA-2026:59546
- https://access.redhat.com/errata/RHSA-2026:57649
- https://access.redhat.com/errata/RHSA-2026:59562
- https://access.redhat.com/errata/RHSA-2026:49712
- https://access.redhat.com/security/cve/CVE-2026-27137
- https://bugzilla.redhat.com/show_bug.cgi?id=2445345
- https://www.cve.org/CVERecord?id=CVE-2026-27137
- https://nvd.nist.gov/vuln/detail/CVE-2026-27137
- https://go.dev/cl/752182
- https://go.dev/issue/77952
- https://groups.google.com/g/golang-announce/c/EdhZqrQ98hk
- https://pkg.go.dev/vuln/GO-2026-4599
- https://access.redhat.com/security/cve/CVE-2026-33810
- https://bugzilla.redhat.com/show_bug.cgi?id=2456335
- https://www.cve.org/CVERecord?id=CVE-2026-33810
- https://nvd.nist.gov/vuln/detail/CVE-2026-33810
- https://go.dev/cl/763763
- https://go.dev/issue/78332
- https://groups.google.com/g/golang-announce/c/0uYbvbPZRWU
- https://pkg.go.dev/vuln/GO-2026-4866
- https://access.redhat.com/errata/RHSA-2026:60354
- https://access.redhat.com/errata/RHSA-2026:60315
- https://access.redhat.com/errata/RHSA-2026:60387
- https://access.redhat.com/errata/RHSA-2026:60520
- https://access.redhat.com/errata/RHSA-2026:61253
- https://access.redhat.com/errata/RHSA-2026:61245
- https://pkg.go.dev
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39821.json
- https://access.redhat.com/errata/RHSA-2026:63134
- https://access.redhat.com/errata/RHSA-2026:65534
- https://access.redhat.com/errata/RHSA-2026:65359
- https://access.redhat.com/errata/RHSA-2026:65886
- https://access.redhat.com/errata/RHSA-2026:65153
- https://access.redhat.com/errata/RHSA-2026:65126
- https://access.redhat.com/errata/RHSA-2026:62549
- https://access.redhat.com/errata/RHSA-2026:66016
- https://access.redhat.com/errata/RHSA-2026:66432
- https://access.redhat.com/errata/RHSA-2026:66022
- https://access.redhat.com/errata/RHSA-2026:67149
- https://access.redhat.com/errata/RHSA-2026:67160
- https://access.redhat.com/errata/RHSA-2026:67159
- https://access.redhat.com/errata/RHSA-2026:66350
- https://access.redhat.com/errata/RHSA-2026:67517
- https://access.redhat.com/errata/RHSA-2026:67319
- https://access.redhat.com/errata/RHSA-2026:67287
- https://access.redhat.com/errata/RHSA-2026:65851
- https://access.redhat.com/errata/RHSA-2026:68504