CVE-2026-126361 Astro: XSS via attribute injection in dynamic tag names
Untrusted data used as element names can inject event-handler markup into Astro pages, enabling XSS; Astro site developers should care.
- 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
- Harmful if only installed
- No
- Needs a specific call
- Yes
- Fix
- None listed
What is CVE-2026-126361?
CVE-2026-126361 is a low-severity cross-site scripting vulnerability in withastro astro, published on 12 Nov 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
Astro is a web framework for content-driven websites. Prior to 7.4.5, Astro rendered a string used as a dynamic element name as raw HTML after applying an incomplete character filter. A / in the string could make an HTML parser treat the remainder as attributes, allowing untrusted element-name input to inject event-handler markup. The .astro dynamic-tag renderer, JSX renderer, and MDX renderer were affected, and exploitation required an application to use request-controlled or stored untrusted data as all or part of an element name. This issue is fixed in version 7.4.5.
Which versions are affected by CVE-2026-126361?
An affected version is only exploitable if your software uses the vulnerable function or option. Many projects that include it are not exposed.
How do I fix CVE-2026-126361?
No fix has been published for CVE-2026-126361 yet. Limit exposure of the affected software until one is available.
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-2026-126361 being exploited?
There is no known exploitation of CVE-2026-126361 in the wild and no public exploit code.
Sources
Also known as GHSA-mh32-jxcr-mh9f.