# 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.

- **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:** No
- **Published:** 12 Nov 2026
- **Updated:** 12 Nov 2026
- **Also known as:** GHSA-mh32-jxcr-mh9f

## 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.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation), CWE-184 (Incomplete List of Disallowed Inputs)

## 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.

## Is CVE-2026-126361 being exploited?

There is no known exploitation of CVE-2026-126361 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-126361 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-126361 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 product: withastro astro. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-126361/ (Markdown: https://insights.sbomify.com/CVE-2026-126361/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-126361
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126361
- OSV: https://osv.dev/vulnerability/CVE-2026-126361

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-126361/
Summaries are generated and may contain mistakes; the official description above is the record.