MediumCVE-2026-114128

    Astro: Reflected/Stored XSS via unescaped <script>/<style> tag content in JSX/MDX rendering (CVE-2026-114128)

    Published Last modified Sources: CVE.org, Hersteller

    What is affected, what to do

    Update Withastro Astro to version 7.3.2.

    Affected
    • Withastro Astro lt *..7.3.2
    Fixed in
    • Withastro Astro 7.3.2

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    6.5

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: Vendor (CNA), CVSS v3

    6.5

    CVSS v3

    Severity Medium on the scale from 0 to 10.

    Source: CVE.org, Hersteller

    —

    EPSS score

    No value is available for this vulnerability.

    Show all metrics
    Severity
    Medium
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    62.50 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

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    no public PoC known
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    6.5 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    6.5
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-79

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    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 astro@7.3.2.

    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.

    Source: NVD (NIST), cvelistv5, GitHub Security Advisories

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    VendorProductAffected versionsFixed in
    withastroastro
    • < 7.3.2
    • 7.3.2
    npmastro
    • < 7.3.2
    • 7.3.2

    Weakness classes (CWE)

    • CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

      Base

      The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

      Entry at MITRE CWE-79

    References & sources

    • github.comwithastro/astro/security/advisories/GHSA-98hj-9722-w3j8x_refsource_CONFIRM
    • github.comwithastro/astro/pull/17896x_refsource_MISC
    • github.comwithastro/astro/commit/a548223607b9bb146d5d90ddda495343f9a2a739x_refsource_MISC
    • github.comwithastro/astro/releases/tag/astro@7.3.2x_refsource_MISC

    Reanalysis & status changes

    Chronological NVD audit events for this CVE — reanalyses, CVSS updates, CPE diffs.

    1. New CVE Receivedsecurity-advisories@github.com

      • Description: after 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.
      • CVSS V3.1: after AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
      • CWE: after CWE-79
      • Affected: after New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/114xxx/CVE-2026-114128.json">CVE-2026-114128</a>
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