# 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.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N`)
- **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:** Yes
- **Published:** 12 Aug 2026
- **Updated:** 14 Aug 2026
- **Also known as:** CLSA-2026-1790089254, CLSA-2026-1790089283, CLSA-2026-1790105671, CLSA-2026-1792161565, CLSA-2026-1792161566, CLSA-2026-1792161567, CLSA-2026-1792161708, CLSA-2026-1792161710, CLSA-2026-1792161711, CLSA-2026-1792161762, CLSA-2026-1792161796, CLSA-2026-1792161797, CLSA-2026-1792161798, CLSA-2026-1792161861, CLSA-2026-1792161862, CLSA-2026-1792161864, GHSA-4g3v-8h47-v7g6

## 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 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-73422?

2 open source packages ship an affected version, including astro.


| Package | Ecosystem | 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.

## Is CVE-2026-73422 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-73422 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-73422 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-73422 exists.

Affected packages and fixed versions:
- astro (npm): affected from 2.9.0; fixed in 7.1.0
- astro (npm): affected from 2.9.0; fixed in 7.1.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-73422/ (Markdown: https://insights.sbomify.com/CVE-2026-73422/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-73422
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-73422
- OSV: https://osv.dev/vulnerability/CVE-2026-73422

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-73422/
Summaries are generated and may contain mistakes; the official description above is the record.