Astro: Reflected/Stored XSS via unescaped <script>/<style> tag content in JSX/MDX rendering

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Astro is a web framework for content-driven websites. Prior to 7.3.2, Astro's JSX and MDX rendering pipeline treats string children of script and style elements as trusted HTML without distinguishing compiler-generated literal content from dynamic expression values. An application that passes attacker-controlled data directly as a dynamic child can allow a value containing a closing script or style tag to terminate the element and inject arbitrary HTML and JavaScript. Other JSX expression contexts escape dynamic strings automatically; the issue is limited to script and style children rendered through the astro:jsx renderer, including MDX components. Successful exploitation can produce reflected or stored cross-site scripting under the application's origin. This issue is fixed in 7.3.2.

Source published

21 Oct 2026 17:32:28 UTC

Source modified

23 Oct 2026 15:11:02 UTC

Observed here

23 Oct 2026 16:48:20 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

Astro is a web framework for content-driven websites. Prior to 7.3.2, Astro's JSX and MDX rendering pipeline treats string children of script and style elements as trusted HTML without distinguishing compiler-generated literal content from dynamic expression values. An application that passes attacker-controlled data directly as a dynamic child can allow a value containing a closing script or style tag to terminate the element and inject arbitrary HTML and JavaScript. Other JSX expression contexts escape dynamic strings automatically; the issue is limited to script and style children rendered through the astro:jsx renderer, including MDX components. Successful exploitation can produce reflected or stored cross-site scripting under the application's origin. This issue is fixed in 7.3.2.

Source published

Oct 21, 2026, 5:32:28 PM (timezone not stated)

Source modified

Oct 23, 2026, 3:11:02 PM (timezone not stated)

Observed here

7 Nov 2026 04:35:46 UTC

Source terms

ENISA EUVD · source terms and attribution apply

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

Astro is a web framework for content-driven websites. Prior to 7.3.2, Astro's JSX and MDX rendering pipeline treats string children of script and style elements as trusted HTML without distinguishing compiler-generated literal content from dynamic expression values. An application that passes attacker-controlled data directly as a dynamic child can allow a value containing a closing script or style tag to terminate the element and inject arbitrary HTML and JavaScript. Other JSX expression contexts escape dynamic strings automatically; the issue is limited to script and style children rendered through the astro:jsx renderer, including MDX components. Successful exploitation can produce reflected or stored cross-site scripting under the application's origin. This issue is fixed in 7.3.2.

Source published

21 Oct 2026 18:17:25 UTC

Source modified

23 Oct 2026 15:17:25 UTC

Observed here

25 Oct 2026 05:17:18 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

## Summary Astro's JSX and MDX rendering pipeline treated string children of `<script>` and `<style>` elements as trusted HTML. When a dynamic value was passed through a JSX expression, such as `<script>{value}</script>`, an attacker-controlled value containing `</script>` or `</style>` could terminate the element and inject arbitrary HTML and JavaScript. Other JSX expression contexts escaped dynamic strings automatically. This behavior was limited to `<script>` and `<style>` children rendered through Astro's `astro:jsx` renderer, including MDX components. ## Details The affected rendering paths marked all string children of `<script>` and `<style>` elements as safe HTML, without distinguishing literal content generated by the compiler from dynamic expression values. An application was vulnerable when attacker-controlled data, such as a query parameter or CMS field, was interpolated directly into one of these elements. For example, a value containing `</script><script>alert(1)</script>` passed to `<script>{value}</script>` was emitted without escaping. The browser interpreted the first closing tag as markup and executed the injected script. The fix preserves raw rendering for literal script and style content while escaping dynamic string children like other JSX expression values. ## Impact Affected applications could be vulnerable to reflected or stored cross-site scripting. Exploitation required an application to pass attacker-controlled data directly as a dynamic child of a `<script>` or `<style>` element in MDX or through the `astro:jsx` runtime. Successful exploitation allowed arbitrary JavaScript execution in the victim's browser under the application's origin. ## Patches This issue is patched in `[email protected]`. ## Workarounds Do not interpolate untrusted dynamic values directly into `<script>` or `<style>` element children. Applications that cannot upgrade should validate and contextually encode these values before rendering them. ## Credit Reported by [@RKasai127](https://github.com/RKasai127).

Source published

22 Oct 2026 16:30:26 UTC

Source modified

22 Oct 2026 16:45:03 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

Publisher rating · MODERATE