Microsoft Authentication Library (MSAL) for Node.js Spoofing Vulnerability
Published September 8, 2026Updated September 8, 2026
Source data
Overview
Authentication bypass by capture-replay in Microsoft Authentication Library (MSAL) for Node.js allows an unauthorized attacker to perform spoofing over a network.
Impact & technical details
Spoofing
According to the CVSS metric, the attack complexity is high (AC:H). What does that mean for this vulnerability? Successful exploitation requires an attacker to first obtain a valid ID token issued for the victim and the same application, and then replay it through a separate authentication flow. These prerequisites make exploitation more difficult.
What action should customers take to address this vulnerability? Customers should update the @azure/msal-node dependency in each affected application to version 5.6.0 or a later compatible version. From the application's project directory, run npm install @azure/msal-node@^5.6.0 --save , then rebuild, test, and redeploy the application using the organization's standard deployment process. See the MSAL Node v5.6.0 release notes and the @azure/msal-node package on npm for additional information.
According to the CVSS metrics, successful exploitation of this vulnerability could lead to major loss of confidentiality (C:H), and integrity (I:H), but could lead to no loss of availability (A:N). What does that mean for this vulnerability? Exploiting this vulnerability could allow an attacker to view highly sensitive user information and modify data, but they cannot affect the availability of the service.
- CVSS base score
- 7.4 / 10
- CVSS vector
- CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C
Highest base score supplied by MSRC for this record; the vector belongs to that score. Ratings can vary by product. Microsoft Important is displayed as High; Moderate is displayed as Medium.
Affected products
- Microsoft Authentication Library (MSAL) for Node.js
Source guidance
Remediation
- Release Notes
Patch availability is not confirmed by this dataset. Consult the vendor before selecting a remediation.
GTP recommendation · Rule-based guidance
Recommended next step
Review affected Microsoft products and apply the applicable security updates through your organization's normal patch-management process. Confirm availability and prerequisites in the Microsoft advisory.
Authoritative sources & updates
Findings and update information come from the linked publishers. GTP compiles the public record and provides the recommendation above. CVSS ratings shown here come from Microsoft. NVD references provide additional public context.
Managed by GTP?
Griffin Technology Partners managed customers may receive additional environment-specific security guidance and remediation assistance through their managed services relationship.
Security bulletins are provided for informational purposes and compiled from authoritative public sources. Vulnerability applicability varies by environment. Validate affected products, configuration, compatibility requirements, and vendor guidance before making production changes.