CVE-2026-42506 Invoking incorrect handling of namespaced elements in foreign content in golang.org/x/net/html

Medium 6.1 Published 22 May 2026 Updated 22 May 2026

Attackers can execute XSS in applications sanitizing HTML via the Go net/html library due to incorrect handling of namespaced elements.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: Available

What is CVE-2026-42506?

CVE-2026-42506 is a medium-severity cross-site scripting vulnerability in golang.org/x/net/html, published on 22 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official 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.

Weakness: CWE-79

Which versions are affected by CVE-2026-42506?

1 open source package ship an affected version, including golang.org/x/net. It affects 1 product.

Package	Affected	Fixed in
`golang.org/x/net` Go	All versions	`0.55.0`

Products include Golang Net.

How do I fix CVE-2026-42506?

Upgrade golang.org/x/net to 0.55.0 or later.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2026-42506 being exploited?

There is no known exploitation of CVE-2026-42506 in the wild and no public exploit code.

Sources

Also known as AZL-87152, AZL-87209, AZL-87323, AZL-87341, AZL-87363, AZL-87432 and 1369 more.