What’s Vulnerable › Vulnerabilities

CVE-2026-27136: Invoking duplicate attributes can cause XSS in golang.org/x/net/html

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-05-22 · updated 2026-07-23
• Weakness: CWE-1021

Description

Parsing arbitrary HTML which is then rendered using Render can result in an unexpected HTML tree. This can be leveraged to execute XSS attacks in applications that attempt to sanitize input HTML before rendering.

Affected products

• golang.org/x/net/html: before 0.55.0 — fixed in 0.55.0
• Golang.Org/X/Net: before 0.55.0 — fixed in 0.55.0

How to fix

Upgrade to a fixed version: golang.org/x/net/html 0.55.0; Golang.Org/X/Net 0.55.0. Check the vendor advisory for mitigations.

References

• https://go.dev/cl/781685
• https://go.dev/issue/79575
• https://groups.google.com/g/golang-announce/c/iI-mYSI0lu8
• https://pkg.go.dev/vuln/GO-2026-5030

Get alerted when CVE-2026-27136 or the next vulnerability affects your stack