6.1

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-44580

CVE-2026-44580: Next.js: Cross-site scripting in beforeInteractive scripts with untrusted input

Next.js is a React framework for building full-stack web applications. From 13.0.0 to before 15.5.16 and 16.2.5, applications that use beforeInteractive scripts together with untrusted content can be vulnerable to cross-site scripting. In affected versions, serialized script content was not escaped safely before being embedded into the document, which could allow attacker-controlled input to break out of the intended script context and execute arbitrary JavaScript in a visitor's browser. This vulnerability is fixed in 15.5.16 and 16.2.5.

(GitHub Advisory)

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CVE-2026-44580

CVE-2026-44580:

6.1

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
next	npm	>= 13.0.0, < 15.5.16	15.5.16
next	npm	>= 16.0.0, < 16.2.5	16.2.5

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability exists in the next/script component, specifically within the Script function in packages/next/src/client/script.tsx. The advisory states that beforeInteractive scripts with untrusted input are vulnerable due to improper escaping. By analyzing the commits between the vulnerable version 16.2.4 and the patched version 16.2.5, I identified the security patch in commit 66f6017f157ae19eb30522105c789999de2de7af. The patch explicitly shows that the dangerouslySetInnerHTML prop was being populated with data from JSON.stringify without any escaping. The fix introduces a call to htmlEscapeJsonString to sanitize the serialized properties before they are embedded in the inline script. This directly addresses the described XSS vulnerability. Therefore, the Script function is the vulnerable function, as it is responsible for this unsafe serialization.

Vulnerable functions

Script

packages/next/src/client/script.tsx

The `Script` component is vulnerable to cross-site scripting. When used with the `beforeInteractive` strategy, it serializes script properties into an inline script using `JSON.stringify` without proper HTML escaping. If attacker-controlled data is passed as a property to the `next/script` component, it can break out of the intended script context and execute arbitrary JavaScript.

Vulnerability Intelligence
Miggo AI

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WAF Protection Rules

WAF Rule

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Reasoning

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