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Vulnerabilities

Security incident · CVE-2026-114128

Astro: Reflected/Stored XSS via unescaped / tag content in JSX/MDX rendering

Published Oct 22, 2026 · catalog updated Oct 22, 2026 · Astro: Reflected/Stored XSS via

Last checked Nov 6, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-114128. EPSS is 0.32%. Act only if a listed version of Astro: Reflected/Stored XSS via is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Astro: Reflected/Stored XSS via).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium6.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.32%
Remediation
Version ranges on file
Affected products
npm astro · package npm

## Summary Astro's JSX and MDX rendering pipeline treated string children of and elements as trusted HTML. When a dynamic value was passed through a JSX expression, such as , an attacker-controlled value containing or could terminate the element and inject arbitrary HTML and JavaScript. Other JSX expression contexts escaped dynamic strings automatically. This behavior was limited to and children rendered through Astro's renderer, including MDX components. ## Details The affected rendering paths marked all string children of and 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 passed to 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 or element in MDX or through the runtime. Successful exploitation allowed arbitrary JavaScript execution in the victim's browser under the application's origin. ## Patches This issue is patched in . ## Workarounds Do not interpolate untrusted dynamic values directly into or element children. Applications that cannot upgrade should validate and contextually encode these values before rendering them. ## Credit Reported by [@RKasai127](https://github.com/RKasai127).

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • npm astro< 7.3.2
  • package npmversion unspecified

How to fix CVE-2026-114128

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-114128. EPSS is 0.32%. Act only if a listed version of Astro: Reflected/Stored XSS via is installed.

Which versions are affected?

Compare what you have installed with < 7.3.2. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-79: Cross-site Scripting (XSS). EPSS 0.32%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 22, 2026 · GitHub Advisory Database

    Detected

    ## Summary Astro's JSX and MDX rendering pipeline treated string children of and elements as trusted HTML. When a dynamic value was passed through a JSX expression, such as , an attacker-controlled value containing or could terminate the element and inject arbitrary HTML and JavaScript. Other JSX expression contexts escaped dynamic strings automatically. This behavior was limited to and children r

  2. Oct 22, 2026 · GitHub Advisory Database

    Updated

    ## Summary Astro's JSX and MDX rendering pipeline treated string children of and elements as trusted HTML. When a dynamic value was passed through a JSX expression, such as , an attacker-controlled value containing or could terminate the element and inject arbitrary HTML and JavaScript. Other JSX expression contexts escaped dynamic strings automatically. This behavior was limited to and children r

Sources

  • CVE.orgVulnerability recordCVE-2026-114128

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-114128

    30-day exploitation probability 0.32%

    first.org
  • GitHub Advisory DatabasePackage advisoryGHSA-98hj-9722-w3j8

    Astro: Reflected/Stored XSS via unescaped / tag content in JSX/MDX rendering

    github.com
  • GitLab Advisory DatabasePackage advisoryCVE-2026-114128

    Astro's JSX and MDX rendering pipeline treated string children of and elements as trusted HTML. When a dynamic value was passed through a JSX expression, such as {value} , an attacker-controlled value containing or could terminate the element and inject arbitrary HTML and JavaScript. Other JSX expression contexts escaped dynamic strings automatically. This behavior was limited to and children rend

    advisories.gitlab.com
  • Snyk Vulnerability DatabasePackage advisorySNYK-JS-ASTRO-21431491

    Cross-site Scripting (XSS)

    security.snyk.io

References

Freshness

Last verified in this catalog Nov 6, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSNov 6, 2026
  • GitLab Advisory DatabaseOct 27, 2026
  • Snyk Vulnerability DatabaseOct 25, 2026
  • GitHub Advisory DatabaseOct 23, 2026
  • CVE.orgOct 23, 2026