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CVE-2026-84003: Microsoft Authentication Library (MSAL) for Node.js Spoofing Vulnerability

• Severity: high (CVSS 7.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-08 · updated 2026-10-31
• Weakness: CWE-294

Description

Authentication bypass by capture-replay in Microsoft Authentication Library (MSAL) for Node.js allows an unauthorized attacker to perform spoofing over a network.

Affected products

• Microsoft Azure/Msal-Node: before 5.6.0 — fixed in 5.6.0
• Microsoft Authentication Library (MSAL) for Android: from 1.0.0 before 5.6.0 — fixed in 5.6.0

How to fix

Upgrade to a fixed version: Microsoft Azure/Msal-Node 5.6.0; Microsoft Authentication Library (MSAL) for Android 5.6.0. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-84003

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