CVE-2026-73422 Astro: Reflected XSS via unescaped View Transition animation properties
Attackers can inject arbitrary JavaScript via unescaped View Transition animation properties in Astro, leading to code execution and data theft.
- 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-2026-73422?
CVE-2026-73422 is a medium-severity cross-site scripting vulnerability in withastro astro, published on 12 Aug 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. From 2.9.0 until 7.1.0, Astro's server-side View Transition CSS generator interpolates animation properties into an inline style element without escaping them for CSS and HTML contexts. An attacker-controlled View Transition animation value such as duration can terminate the generated style element and inject arbitrary HTML or JavaScript. The affected code is packages/astro/src/runtime/server/transition.ts; renderTransition passes sheet.toString() into markHTMLString(), while addAnimationProperty serializes duration through toTimeValue() and also handles easing, direction, delay, fillMode, and name. Exploitation requires an on-demand or server-rendered route to pass attacker-controlled data into a View Transition animation definition and can execute arbitrary JavaScript in the affected application's origin, allowing access to sensitive page data and authenticated actions available to the victim. This issue is fixed in version 7.1.0.
Weakness: CWE-79
Which versions are affected by CVE-2026-73422?
2 open source packages ship an affected version, including astro.
| Package | Affected | Fixed in |
|---|---|---|
astro npm | From 2.9.0 | 7.1.0 |
astro npm | From 2.9.0 | 7.1.0 |
How do I fix CVE-2026-73422?
Upgrade astro to 7.1.0 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-2026-73422 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-73422 exists.
Sources
Also known as CLSA-2026-1790089254, CLSA-2026-1790089283, CLSA-2026-1790105671, CLSA-2026-1792161565, CLSA-2026-1792161566, CLSA-2026-1792161567 and 11 more.