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: 0.01%• Percentile: 1%

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

• go standard library•html/template

  < 1.25.10 | ≥ 1.26.0-0, < 1.26.3

• golang•go

  < 1.25.10 | ≥ 1.26.0, < 1.26.3

• Go•stdlib

  ≥ 1.26.0-0, < 1.26.3

References (4)

• 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