---
id: CVE-2026-39823
title: >-
  html/template: golang: Go html/template: Cross-Site Scripting via improper URL
  escaping in meta tag content (CVE-2026-39823)
summary: >-
  A flaw was found in the `html/template` package of Go. A remote attacker could
  exploit this vulnerability by inserting ASCII whitespaces around the equals
  sign (`=`) within a URL's content attribute inside a `<meta>` tag. This
  improper esc…
severity: medium
cvss: 5.4
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N'
cvssSource: vendor
cwe: CWE-79
vendor: Red Hat
product: Red Hat OpenShift Container Platform 4
affected:
  - assisted_installer_for_red_hat_openshift_container_platform 2
  - builds_for_red_hat_openshift
  - cert_manager_operator_for_red_hat_openshift
  - compliance_operator
  - confidential_compute_attestation
  - cryostat 4
  - custom_metric_autoscaler_operator_for_red_hat_openshift
  - deployment_validation_operator
  - external_secrets_operator_for_red_hat_openshift
  - file_integrity_operator
  - gatekeeper 3
  - logging_subsystem_for_red_hat_openshift
  - logical_volume_manager_storage
  - migration_toolkit_for_applications 8
  - migration_toolkit_for_containers
  - multiarch_tuning_operator
  - multicluster_engine_for_kubernetes
  - multicluster_global_hub
  - network_observability_operator
  - openshift_developer_tools_and_services
  - openshift_lightspeed
  - openshift_pipelines
  - openshift_serverless
  - openshift_service_mesh 2
  - openshift_service_mesh 3
  - power_monitoring_for_red_hat_openshift
  - 3scale_api_management_platform 2
  - advanced_cluster_management_for_kubernetes 2
  - advanced_cluster_security 4
  - ansible_automation_platform 2
  - ceph_storage 5
  - ceph_storage 6
  - ceph_storage 7
  - ceph_storage 8
  - ceph_storage 9
  - certification_program_for_red_hat_enterprise_linux 9
  - connectivity_link 1
  - developer_hub
  - edge_manager 1
  - enterprise_linux 10
patched:
  - enterprise_linux_appstream_eus_v_10_0
  - enterprise_linux_appstream_v_10
  - enterprise_linux_appstream_v_8
  - enterprise_linux_appstream_e4s_v_9_2
  - enterprise_linux_appstream_e4s_v_9_4
  - enterprise_linux_appstream_eus_v_9_6
  - enterprise_linux_appstream_v_9
  - openshift_api_for_data_protection 1.6
  - hardened_images
  - openshift_distributed_tracing 3.10.2
  - multicluster_engine_for_kubernetes 2.11
published: '2026-05-07'
updated: '2026-09-21'
sourceUpdated: '2026-09-21T17:36:40+00:00'
source: CSAF
sourceUrl: 'https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39823.json'
references:
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39823.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-39823'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2467811'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-39823'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-39823'
  - url: 'https://go.dev/cl/769920'
  - url: 'https://go.dev/issue/78913'
  - url: 'https://groups.google.com/g/golang-announce/c/qcCIEXso47M'
  - url: 'https://pkg.go.dev/vuln/GO-2026-4982'
  - url: 'https://access.redhat.com/errata/RHSA-2026:49702'
  - url: 'https://access.redhat.com/errata/RHSA-2026:22120'
  - url: 'https://access.redhat.com/errata/RHSA-2026:22112'
  - url: 'https://access.redhat.com/errata/RHSA-2026:61253'
  - url: 'https://access.redhat.com/errata/RHSA-2026:57649'
  - url: 'https://access.redhat.com/errata/RHSA-2026:49712'
  - url: 'https://access.redhat.com/errata/RHSA-2026:22121'
  - url: 'https://access.redhat.com/errata/RHSA-2026:43692'
  - url: 'https://access.redhat.com/errata/RHSA-2026:23262'
  - url: 'https://access.redhat.com/errata/RHSA-2026:23264'
  - url: 'https://access.redhat.com/errata/RHSA-2026:50205'
  - url: 'https://access.redhat.com/errata/RHSA-2026:57194'
tags:
  - csaf
  - vex
  - red-hat
  - osv
  - go
epss: 0.00333
epssPercentile: 0.23711
aliases:
  - GO-2026-4982
  - BIT-golang-2026-39823
ecosystem: go
ingestedAt: '2026-08-26T19:27:02.507Z'
---

## Overview

A flaw was found in the `html/template` package of Go. A remote attacker could exploit this vulnerability by inserting ASCII whitespaces around the equals sign (`=`) within a URL's content attribute inside a `<meta>` tag. This improper escaping could lead to Cross-Site Scripting (XSS), allowing the attacker to execute malicious scripts in the user's browser.

## Vendor advisories

- **RHSA-2026:49702** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v. 10.0) · released 2026-08-03 · [advisory](https://access.redhat.com/errata/RHSA-2026:49702)
- **RHSA-2026:22120** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10) · released 2026-06-01 · [advisory](https://access.redhat.com/errata/RHSA-2026:22120)
- **RHSA-2026:22112** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 8) · released 2026-06-01 · [advisory](https://access.redhat.com/errata/RHSA-2026:22112)
- **RHSA-2026:61253** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream E4S (v.9.2) · released 2026-08-31 · [advisory](https://access.redhat.com/errata/RHSA-2026:61253)
- **RHSA-2026:57649** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream E4S (v.9.4) · released 2026-08-20 · [advisory](https://access.redhat.com/errata/RHSA-2026:57649)
- **RHSA-2026:49712** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v.9.6) · released 2026-08-03 · [advisory](https://access.redhat.com/errata/RHSA-2026:49712)
- **RHSA-2026:22121** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9) · released 2026-06-01 · [advisory](https://access.redhat.com/errata/RHSA-2026:22121)
- **RHSA-2026:43692** · Red Hat · fixed in: OpenShift API for Data Protection 1.6 · released 2026-07-22 · [advisory](https://access.redhat.com/errata/RHSA-2026:43692)
- **RHSA-2026:23262** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-06-04 · [advisory](https://access.redhat.com/errata/RHSA-2026:23262)
- **RHSA-2026:23264** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-06-04 · [advisory](https://access.redhat.com/errata/RHSA-2026:23264)
- **RHSA-2026:50205** · Red Hat · fixed in: Red Hat OpenShift distributed tracing 3.10.2 · released 2026-08-04 · [advisory](https://access.redhat.com/errata/RHSA-2026:50205)
- **Red Hat VEX** · Moderate · affected: Assisted Installer for Red Hat OpenShift Container Platform 2, Builds for Red Hat OpenShift, cert-manager Operator for Red Hat OpenShift, Compliance Operator, Confidential Compute Attestation, Cryostat 4, … · no fix planned: Red Hat Enterprise Linux 10, Assisted Installer for Red Hat OpenShift Container Platform 2, Builds for Red Hat OpenShift, cert-manager Operator for Red Hat OpenShift, … · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39823.json)

**html/template: golang: Go html/template: Cross-Site Scripting via improper URL escaping in meta tag content** — rated Moderate by Red Hat. Released 2026-05-07, updated 2026-09-21.

Affected:

- Assisted Installer for Red Hat OpenShift Container Platform 2
- Builds for Red Hat OpenShift
- cert-manager Operator for Red Hat OpenShift
- Compliance Operator
- Confidential Compute Attestation
- Cryostat 4
- Custom Metric Autoscaler operator for Red Hat Openshift
- Deployment Validation Operator
- External Secrets Operator for Red Hat OpenShift
- File Integrity Operator
- Gatekeeper 3
- Logging Subsystem for Red Hat OpenShift
- Logical Volume Manager Storage
- Migration Toolkit for Applications 8
- Migration Toolkit for Containers
- Multiarch Tuning Operator
- Multicluster Engine for Kubernetes
- Multicluster Global Hub
- Network Observability Operator
- OpenShift Developer Tools and Services
- OpenShift Lightspeed
- OpenShift Pipelines
- OpenShift Serverless
- OpenShift Service Mesh 2
- OpenShift Service Mesh 3
- Power monitoring for Red Hat OpenShift
- Red Hat 3scale API Management Platform 2
- Red Hat Advanced Cluster Management for Kubernetes 2
- Red Hat Advanced Cluster Security 4
- Red Hat Ansible Automation Platform 2
- Red Hat Ceph Storage 5
- Red Hat Ceph Storage 6
- Red Hat Ceph Storage 7
- 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 Edge Manager 1
- Red Hat Enterprise Linux 10

Fixed:

- Red Hat Enterprise Linux AppStream EUS (v. 10.0)
- Red Hat Enterprise Linux AppStream (v. 10)
- Red Hat Enterprise Linux AppStream (v. 8)
- Red Hat Enterprise Linux AppStream E4S (v.9.2)
- Red Hat Enterprise Linux AppStream E4S (v.9.4)
- Red Hat Enterprise Linux AppStream EUS (v.9.6)
- Red Hat Enterprise Linux AppStream (v. 9)
- OpenShift API for Data Protection 1.6
- Red Hat Hardened Images
- Red Hat OpenShift distributed tracing 3.10.2
- multicluster engine for Kubernetes 2.11

No fix planned:

- Red Hat Enterprise Linux 10
- Assisted Installer for Red Hat OpenShift Container Platform 2
- Builds for Red Hat OpenShift
- cert-manager Operator for Red Hat OpenShift
- Compliance Operator
- Confidential Compute Attestation
- Cryostat 4
- Custom Metric Autoscaler operator for Red Hat Openshift
- Deployment Validation Operator
- External Secrets Operator for Red Hat OpenShift
- File Integrity Operator
- Gatekeeper 3
- Logging Subsystem for Red Hat OpenShift
- Logical Volume Manager Storage
- Migration Toolkit for Applications 8
- Migration Toolkit for Containers
- Multiarch Tuning Operator
- Multicluster Engine for Kubernetes
- Multicluster Global Hub
- Network Observability Operator
- OpenShift Developer Tools and Services
- OpenShift Lightspeed
- OpenShift Pipelines
- OpenShift Serverless
- OpenShift Service Mesh 2
- OpenShift Service Mesh 3
- Power monitoring for Red Hat OpenShift
- Red Hat 3scale API Management Platform 2
- Red Hat Advanced Cluster Management for Kubernetes 2
- Red Hat Advanced Cluster Security 4
- Red Hat Ansible Automation Platform 2
- Red Hat Ceph Storage 5
- Red Hat Ceph Storage 6
- Red Hat Ceph Storage 7
- 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 Edge Manager 1

Not affected:

- OpenShift API for Data Protection 1.6
- Red Hat OpenShift distributed tracing 3.10.2
- multicluster engine for Kubernetes 2.11
- Red Hat OpenShift Container Platform 4

## Remediation

For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258 https://access.redhat.com/errata/RHSA-2026:49702
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258 https://access.redhat.com/errata/RHSA-2026:22120
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258 https://access.redhat.com/errata/RHSA-2026:22112

Workarounds / mitigations:

- Ensure that user-supplied URLs are validated and sanitized before being passed to Go's `html/template` package for rendering in HTML meta tag content attributes. Avoid rendering untrusted URL data directly in meta tag content attributes.

## Package advisory (CVE-2026-39823)

Affected packages:

- `stdlib >= 1.26.0-0, < 1.26.3`

Patched in:

- `stdlib 1.26.3`

Source: https://osv.dev/vulnerability/GO-2026-4982