CVE-2026-39823

Description

CVE-2026-27142 fixed a vulnerability in which URLs were not correctly escaped inside of a <meta> tag's <content> attribute. If the URL content were to insert ASCII whitespaces around the '=' rune inside of the <content> attribute, the escaper would fail to similarly escape it, leading to XSS.

CVSS Metrics

• v3.1•MEDIUM•Score: 6.1CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS Trends

Current EPSS score: 0.31%• Percentile: 25%

Techniques & Countermeasures

• CWE-79•Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

  The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

Affected Systems

• chainguard•aactl

  < 0.4.12-r50 | < 0.4.12-r51

• chainguard•act

  < 0

• chainguard•actions-runner-controller-fips

  < 0.14.1-r2 | < 0.14.1-r1 | < 0

• chainguard•addon-resizer

  < 0

• chainguard•addon-resizer-fips

  < 0

• chainguard•age-fips

  < 1.3.1-r7 | < 0

• chainguard•agentbeat

  < 9.2.7-r7

• chainguard•agentbeat-fips

  < 9.2.7-r6 | < 9.2.7-r7

• chainguard•amazon-cloudwatch-agent

  < 1.300067.0-r2 | < 1.300067.0-r3

• 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-operator

  < 3.4.2-r2

• chainguard•amazon-cloudwatch-agent-operator-fips

  < 3.4.2-r1

• chainguard•amazon-cloudwatch-agent-start-amazon-cloudwatch-agent

  < 0

• chainguard•amazon-cloudwatch-agent-start-amazon-cloudwatch-agent-fips

  < 0

• chainguard•amazon-ecs-agent-fips

  < 1.103.0-r0 | < 1.103.0-r1

• chainguard•amazon-ecs-cni-plugins-fips

  < 0 | < 2024.9.0_git20260306-r2

• chainguard•amazon-eks-ami

  < 0

• chainguard•amazon-eks-ami-fips

  < 0 | < 20260318-r3

• chainguard•amazon-k8s-cni

  < 1.21.1-r6 | < 1.21.1-r7

• chainguard•amazon-k8s-cni-fips

  < 1.21.1-r6

• chainguard•amazon-k8s-cni-init

  < 0

• chainguard•amazon-k8s-cni-init-fips

  < 0

• chainguard•amazon-k8s-cni-init-fips-compat

  < 1.21.1-r6 | < 0

• chainguard•amazon-ssm-agent

  < 0 | < 3.3.3270.0-r14

• chainguard•amazon-ssm-agent-ecs-exec

  < 0 | < 3.3.3270.0-r14

• chainguard•amazon-ssm-agent-ecs-exec-fips

  < 0 | < 3.3.3270.0-r15 | < 3.3.3270.0-r16

• chainguard•amazon-ssm-agent-fips

  < 0 | < 3.3.3270.0-r16

• chainguard•amazon-vpc-cni-plugins-fips

  < 1.3_git20260307-r1 | < 0

• chainguard•ansible-operator

  < 1.42.2-r5 | < 1.42.2-r4

• chainguard•ansible-operator-fips

  < 1.42.2-r5

• chainguard•apache-exporter

  < 1.0.12-r6

• chainguard•apko

  < 1.2.11-r1 | < 1.2.11-r2

• chainguard•apko-fips

  < 1.2.10-r0 | < 1.2.10-r1

• chainguard•apm-server-fips-8.19

  < 8.19.15-r4

• chainguard•apm-server-fips-9.1

  < 9.1.10-r7

• chainguard•apm-server-fips-9.2

  < 0

• chainguard•apm-server-fips-9.3

  < 0

• chainguard•apm-server-fips-9.4

  < 0

• chainguard•argo-cd-3.3-compat

  < 3.3.9-r2

• chainguard•argo-cd-fips-3.0

  < 3.0.23-r7

• chainguard•argo-cd-fips-3.0-compat

  < 3.0.23-r7

• chainguard•argo-cd-fips-3.1

  < 3.1.16-r1

• chainguard•argo-cd-fips-3.1-compat

  < 3.1.16-r1

• chainguard•argo-cd-fips-3.2

  < 3.2.11-r2 | < 3.2.11-r1

• chainguard•argo-cd-fips-3.2-compat

  < 3.2.11-r1

Showing first 50 affected entries in server-rendered view.

References (8)

• https://go.dev/issue/78913
• https://go.dev/cl/769920
• https://groups.google.com/g/golang-announce/c/qcCIEXso47M
• https://pkg.go.dev/vuln/GO-2026-4982
• https://security-tracker.debian.org/tracker/CVE-2026-39823
• https://pkg.go.dev
• https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39823.json
• https://nvd.nist.gov/vuln/detail/CVE-2026-39823