CVE-2026-109461

What it actually does

Origin validation error permits an attacker to bypass intended cross-origin restrictions in authentication flows, resulting in unauthorized disclosure of sensitive authentication-related data over the network.

Why it matters to the business

Organizations face risk of credential or token leakage that could enable account compromise or further attacks, increasing exposure for any applications relying on this library for authentication.

How an attack unfolds

An attacker positioned on the network sends specially crafted authentication requests that exploit insufficient origin checks within the library, allowing interception or direct disclosure of protected information without authentication.

How to fix it

Upgrade to the latest patched version of Microsoft Authentication Library for Node.js as soon as it becomes available from Microsoft; in the interim, review and strengthen origin validation in dependent applications and monitor vendor advisories.

How to confirm the fix worked

Verify the installed library version against the fixed release once published; conduct code and configuration reviews to confirm proper origin enforcement in authentication handlers.

Typical attack path

1. Identify applications using the vulnerable MSAL Node.js library for authentication
2. Craft and send network requests with manipulated or spoofed origins to the authentication endpoints
3. Bypass origin validation to trigger disclosure of sensitive data such as tokens or session information
4. Capture the disclosed data for use in subsequent attacks

How to detect it

Review application and network logs for unexpected cross-origin authentication requests or anomalous responses containing authentication artifacts; correlate with library version data to identify vulnerable instances.

What your security team should do

• Prioritize monitoring Microsoft security updates for MSAL Node.js and schedule immediate upgrades upon release
• Audit all Node.js applications using MSAL to identify exposure and implement compensating controls such as strict CORS policies
• Increase logging around authentication flows to support future detection efforts