golang.org/x/net/idna pre-0.55.0 IDN bug allows silent ASCII/Unicode mix
CVE-2026-39821 Published on May 22, 2026

Invoking failure to reject ASCII-only Punycode-encoded labels in golang.org/x/net/idna
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".

NVD

Vulnerability Analysis

CVE-2026-39821 can be exploited with network access, and requires small amount of user privileges. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality and integrity, and no impact on availability.

Attack Vector:
NETWORK
Attack Complexity:
HIGH
Privileges Required:
LOW
User Interaction:
NONE
Scope:
CHANGED
Confidentiality Impact:
HIGH
Integrity Impact:
HIGH
Availability Impact:
NONE

Weakness Type

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.


Products Associated with CVE-2026-39821

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Affected Versions

Go standard library net/http: Go standard library net/http/internal/http2: golang.org/x/net/idna: Red Hat Ansible Automation Platform 2.5 for RHEL 8: Red Hat Ansible Automation Platform 2.5 for RHEL 9: Red Hat Ansible Automation Platform 2.6 for RHEL 10: Red Hat Ansible Automation Platform 2.6 for RHEL 9: Red Hat Ansible Automation Platform 2.7 for RHEL 10: Red Hat Ansible Automation Platform 2.7 for RHEL 9: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10.0 Extended Update Support: Red Hat Enterprise Linux 10.0 Extended Update Support: Red Hat Enterprise Linux 10.0 Extended Update Support: Red Hat Enterprise Linux 10.0 Extended Update Support: Red Hat Enterprise Linux 10.0 Extended Update Support: Red Hat Enterprise Linux 10.0 Extended Update Support: Red Hat Enterprise Linux 7 Extended Lifecycle Support: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions: Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions: Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions: Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions: Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions: Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions: Red Hat Enterprise Linux 9.6 Extended Update Support: Red Hat Enterprise Linux 9.6 Extended Update Support: Red Hat Enterprise Linux 9.6 Extended Update Support: Red Hat Enterprise Linux 9.6 Extended Update Support: Red Hat Enterprise Linux 9.6 Extended Update Support: Red Hat Enterprise Linux 9.6 Extended Update Support: Red Hat Enterprise Linux 9.6 Extended Update Support: Red Hat OpenShift Container Platform 4.16: Red Hat OpenShift Container Platform 4.20: Red Hat OpenShift Container Platform 4.22: Red Hat OpenStack Platform 16.2: Red Hat Satellite 6.16 for RHEL 8: Red Hat Satellite 6.16 for RHEL 9: Red Hat Satellite 6.17 for RHEL 9: Red Hat Satellite 6.18 for RHEL 9: Red Hat Satellite 6.19 for RHEL 9: Red Hat RHEM 1.0 for RHEL 9: Red Hat RHEM 1.1 for RHEL 10: Red Hat RHEM 1.1 for RHEL 9: Red Hat Streams for Apache Kafka 3.2.1: Cert Manager support for Red Hat OpenShift release 1.19: Red Hat Cluster Observability Operator 1.5.0: Red Hat Cluster Observability Operator 1.5.0: Red Hat Cluster Observability Operator 1.5.0: Red Hat Cluster Observability Operator 1.5.0: Red Hat Cluster Observability Operator 1.5.0: Red Hat Cluster Observability Operator 1.5.0: Red Hat Cluster Observability Operator 1.5.0: Red Hat Cluster Observability Operator 1.5.0: Red Hat Cluster Observability Operator 1.5.0: Red Hat DevWorkspace Operator 0.42: Logging for Red Hat OpenShift 6.0: Logging for Red Hat OpenShift 6.2: Logging Subsystem for Red Hat OpenShift 6.4: Logging Subsystem for Red Hat OpenShift 6.5: Red Hat multicluster engine for Kubernetes 2.11: Red Hat multicluster engine for Kubernetes 2.6: Red Hat multicluster engine for Kubernetes 2.6: Red Hat multicluster engine for Kubernetes 2.6: Red Hat multicluster engine for Kubernetes 2.8: Red Hat multicluster engine for Kubernetes 2.8: Red Hat multicluster engine for Kubernetes 2.8: Red Hat multicluster engine for Kubernetes 2.8: Red Hat multicluster engine for Kubernetes 2.9: Red Hat Multicluster Global Hub 1.5.6: Red Hat Multicluster Global Hub 1.7.0: Red Hat OpenShift API for Data Protection 1.3: Red Hat OpenShift API for Data Protection 1.6: Red Hat Advanced Cluster Management for Kubernetes 2.11: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Management for Kubernetes 2.13: Red Hat Advanced Cluster Security for Kubernetes 4.10: Red Hat Advanced Cluster Security for Kubernetes 4.11: Red Hat Advanced Cluster Security for Kubernetes 4.9: Red Hat Ansible Automation Platform 2.6: Red Hat Ansible Automation Platform 2.7: Red Hat Edge Manager 1.0: Red Hat Edge Manager 1.1: Red Hat Edge Manager 1.1: Red Hat Enterprise Linux AI 3.4: Red Hat Enterprise Linux AI 3.4: Red Hat Enterprise Linux AI 3.4: Red Hat Enterprise Linux AI 3.4: Red Hat Enterprise Linux AI 3.4: Red Hat Enterprise Linux AI 3.4: Red Hat Enterprise Linux AI 3.4: Red Hat Hardened Images: Red Hat Hardened Images: Red Hat Lightspeed (formerly Insights) for Runtimes 1.0: Red Hat Migration Toolkit 1.8: Red Hat Migration Toolkit for Applications 8.1: Red Hat Migration Toolkit for Applications 8.2: Red Hat multicluster global hub 1.4.2: Red Hat multicluster global hub 1.6.0: Red Hat OpenShift AI 2.25: Red Hat OpenShift AI 2.25: Red Hat OpenShift AI 2.25: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift AI 3.4: Red Hat OpenShift Builds 1.7.3: Red Hat OpenShift Builds 1.7.3: Red Hat OpenShift Builds 1.8.1: Red Hat OpenShift Builds 1.8.1: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.18: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat Openshift Data Foundation 4.22: Red Hat OpenShift Dev Spaces 3.29: Red Hat OpenShift distributed tracing 3.10.1: Red Hat OpenShift distributed tracing 3.10.1: Red Hat OpenShift distributed tracing 3.10.1: Red Hat OpenShift distributed tracing 3.10.1: Red Hat OpenShift distributed tracing 3.10.1: Red Hat OpenShift distributed tracing 3.10.1: Red Hat OpenShift distributed tracing 3.10.1: Red Hat OpenShift GitOps 1.19: Red Hat OpenShift GitOps 1.2: Red Hat OpenShift Service Mesh 2.6: Red Hat OpenShift Service Mesh 3.0: Red Hat OpenShift Service Mesh 3.1: Red Hat OpenShift Service Mesh 3.2: Red Hat OpenShift Service Mesh 3.3: Red Hat OpenShift Workload Availability 0.12: Red Hat OpenShift Workload Availability 0.13: Red Hat OpenShift Workload Availability 0.3: Red Hat OpenShift Workload Availability 0.7: Red Hat OpenShift Workload Availability 0.8: Red Hat OpenShift Workload Availability 5.7: Red Hat Quay 3.1: Red Hat Quay 3.12: Red Hat Quay 3.15: Red Hat Quay 3.16: Red Hat Quay 3.17: Red Hat Quay 3.9: Red Hat Satellite 6.18: Red Hat Satellite 6.19: Red Hat Trusted Artifact Signer 1.4: Red Hat Web Terminal 1.11: Red Hat Web Terminal 1.12: Red Hat Web Terminal 1.13: Red Hat Web Terminal 1.14: Red Hat Web Terminal 1.15: Red Hat Web Terminal 1.16: Assisted Installer for Red Hat OpenShift Container Platform 2: Red Hat Compliance Operator: Red Hat Confidential Compute Attestation: Red Hat Confidential Compute Attestation: Red Hat Cryostat 4: Red Hat Deployment Validation Operator: Red Hat ExternalDNS Operator: Red Hat ExternalDNS Operator: External Secrets Operator for Red Hat OpenShift: Red Hat Fence Agents Remediation Operator: Red Hat File Integrity Operator: Red Hat Gatekeeper 3: Red Hat Logical Volume Manager Storage: Red Hat Logical Volume Manager Storage: Red Hat Logical Volume Manager Storage: Red Hat Machine Deletion Remediation Operator: Red Hat Multiarch Tuning Operator: Red Hat Multicluster Engine for Kubernetes: Red Hat Multicluster Engine for Kubernetes: Red Hat Multicluster Engine for Kubernetes: Red Hat Multicluster Engine for Kubernetes: Red Hat Multicluster Engine for Kubernetes: Red Hat Multicluster Engine for Kubernetes: Red Hat Multicluster Engine for Kubernetes: Red Hat Multicluster Engine for Kubernetes: Red Hat Multicluster Engine for Kubernetes: Red Hat Multicluster Engine for Kubernetes: Red Hat Multicluster Engine for Kubernetes: Red Hat Multicluster Engine for Kubernetes: Red Hat Multicluster Engine for Kubernetes: Red Hat Multicluster Engine for Kubernetes: Red Hat Multicluster Engine for Kubernetes: Red Hat Multicluster Engine for Kubernetes: Red Hat Multicluster Engine for Kubernetes: Red Hat Network Observability Operator: Red Hat Node HealthCheck Operator: Red Hat Node HealthCheck Operator: Red Hat Node HealthCheck Operator: Red Hat OpenShift API for Data Protection: Red Hat OpenShift API for Data Protection: Red Hat OpenShift Developer Tools and Services: Red Hat OpenShift Lightspeed: Red Hat OpenShift Pipelines: Red Hat OpenShift Pipelines: Red Hat OpenShift Serverless: Red Hat OpenShift Serverless: Red Hat OpenShift Serverless: Red Hat OpenShift Serverless: Power monitoring for Red Hat OpenShift: Red Hat 3scale API Management Platform 2: Red Hat 3scale API Management Platform 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Advanced Cluster Management for Kubernetes 2: Red Hat Ansible Automation Platform 2: Red Hat Ansible Automation Platform 2: Red Hat Ansible Automation Platform 2: Red Hat Ansible Automation Platform 2: Red Hat Ansible Automation Platform 2: Red Hat Ansible Automation Platform 2: Red Hat Ceph Storage 5: Red Hat Ceph Storage 6: Red Hat Ceph Storage 8: Red Hat Ceph Storage 9: Red Hat Certification Program for Red Hat Enterprise Linux 9: Red Hat Connectivity Link 1: Red Hat Developer Hub: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 7: Red Hat Enterprise Linux 7: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux AI (RHEL AI) 3: Red Hat Hardened Images: Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift AI (RHOAI): Red Hat OpenShift Cluster Manager CLI: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift for Windows Containers: Red Hat OpenShift on AWS: Red Hat OpenShift Virtualization 4: Red Hat OpenShift Virtualization 4: Red Hat OpenStack Platform 16.2: Red Hat OpenStack Platform 16.2: Red Hat OpenStack Platform 17.1: Red Hat OpenStack Platform 17.1: Red Hat OpenStack Platform 17.1: Red Hat OpenStack Platform 17.1: Red Hat OpenStack Platform 18.0: Red Hat OpenStack Platform 18.0: Red Hat Satellite 6: Red Hat Service Interconnect 1: Red Hat Service Interconnect 2: Red Hat Security Profiles Operator: Red Hat Zero Trust Workload Identity Manager: Red Hat Zero Trust Workload Identity Manager - Tech Preview:

Exploit Probability

EPSS
0.66%
Percentile
47.65%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.