6.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2025-50864

CVE-2025-50864: elysia-cors Origin Validation Error

An Origin Validation Error in the elysia-cors library thru 1.3.0 allows attackers to bypass Cross-Origin Resource Sharing (CORS) restrictions. The library incorrectly validates the supplied origin by checking if it is a substring of any domain in the site's CORS policy, rather than performing an exact match. For example, a malicious origin like "notexample.com", "example.common.net" is whitelisted when the site's CORS policy specifies "example.com." This vulnerability enables unauthorized access to user data on sites using the elysia-cors library for CORS validation.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2025-50864

CVE-2025-50864:

6.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
@elysiajs/cors	npm	< 1.3.1	1.3.1

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability analysis focused on the provided commit patch, which clearly shows the remediation of the origin validation error. The commit 9b9eb92e32a7a4b43b6d5108668941701c33e221 modifies the src/index.ts file, specifically within the processOrigin function. The vulnerable code used String.prototype.includes() to check if the incoming request's origin header was a substring of the allowed origins in the CORS policy. This is a flawed approach, as it allows a malicious domain (e.g., notexample.com) to be accepted if a legitimate domain (example.com) is part of its string. The patch replaces this insecure substring check with a strict equality check, ensuring that only explicitly whitelisted origins are granted access. The processOrigin function is the precise location of this flawed logic and is therefore identified as the vulnerable function. This function is called by the main cors plugin logic whenever a request with an Origin header is received.

Vulnerable functions

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WAF Protection Rules

WAF Rule

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Reasoning

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