# CVE-2026-126362: Astro: Reflected XSS via unescaped slot names in @astrojs/svelte

> Attackers can inject HTML via unescaped slot names in Astro Svelte components that render attacker-chosen slots; Astro site developers should care.

- **Severity:** Low 2.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/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
- **Harmful if only installed:** No
- **Needs a specific call:** Yes
- **Fix available:** Yes
- **Published:** 12 Nov 2026
- **Updated:** 12 Nov 2026
- **Also known as:** GHSA-f4j9-crrj-867q

## What is CVE-2026-126362?

CVE-2026-126362 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. From 5.7.3 until 9.1.2, the @astrojs/svelte renderer inserted a named slot into the quoted name attribute of an astro-slot wrapper without HTML escaping. Request-controlled slot names containing a quote could terminate the attribute and inject active HTML. Exploitation required a hydrated Svelte component using a client:* directive and dynamic rendering of the attacker-chosen slot; components that did not render that slot emitted only Astro's escaped fallback content. Both server rendering and client-side hydration used the unsafe slot name. This issue is fixed in version 9.1.2.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-126362?

1 open source package ship an affected version, including @astrojs/svelte.

An affected version is only exploitable if your software uses the vulnerable function or option. Many projects that include it are not exposed.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@astrojs/svelte` | npm | From 5.7.3 | 9.1.2 |

## How do I fix CVE-2026-126362?

Upgrade @astrojs/svelte to 9.1.2 or later.

## Is CVE-2026-126362 being exploited?

There is no known exploitation of CVE-2026-126362 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-126362 and fix it if it is affected.

What it is: CVE-2026-126362 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.
Exploitation: There is no known exploitation of CVE-2026-126362 in the wild and no public exploit code.
Exposure: An affected version is only exploitable if your software uses the vulnerable function or option. Many projects that include it are not exposed.

Affected packages and fixed versions:
- @astrojs/svelte (npm): affected from 5.7.3; fixed in 9.1.2

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-2026-126362/ (Markdown: https://insights.sbomify.com/CVE-2026-126362/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-126362
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126362
- OSV: https://osv.dev/vulnerability/CVE-2026-126362

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-126362/
Summaries are generated and may contain mistakes; the official description above is the record.