# CVE-2026-84003: Microsoft Authentication Library authentication bypass in MSAL for Node.js

Source: https://junglewise.ai/threats/cve-2026-84003-microsoft-authentication-library-authentication-bypass-in-msal  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-08. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-84003 · Severity: high · CVSS 7.4 · Published 2026-09-08

Microsoft Authentication Library (MSAL) for Node.js is used by applications to securely authenticate users and obtain access tokens. A capture-replay authentication bypass vulnerability allows an attacker to impersonate legitimate users and perform unauthorized actions, potentially compromising any system relying on MSAL for authentication.

Technologies: [Microsoft Authentication Library (MSAL) for Node.js](https://junglewise.ai/threats/technologies/authentication-library-msal-for-node-js). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-84003 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-84003 being exploited in the wild.

**How severe is CVE-2026-84003?** High severity, with a CVSS score of 7.4, published 8 September 2026.

**Which products and versions are affected?** Microsoft Authentication Library (MSAL) for Node.js.

**Is there a fix for CVE-2026-84003?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-84003 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-84003?** Check whether you run Microsoft Authentication Library (MSAL) for Node.js or Microsoft Azure\. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is an authentication bypass in MSAL for Node.js that exploits capture-replay attack techniques. An attacker can intercept and replay authentication tokens or credentials to bypass the authentication mechanism and assume the identity of a legitimate user. The attack is network-based and does not require prior authentication or special privileges. This vulnerability allows an attacker to spoof user identity and gain unauthorized access to protected resources. A patch is expected to be available from Microsoft.

## Affected products

- Microsoft Authentication Library (MSAL) for Node.js

## Timeline

- 2026-09-08: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-84003](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-84003)

## Related threats

- [Microsoft Authentication Library (MSAL) for Node.js credential exposure](https://junglewise.ai/threats/cve-2026-108470-insufficiently-protected-credentials-in-microsoft-authentication)
- [Microsoft Authentication Library (MSAL) for Node.js origin validation bypass](https://junglewise.ai/threats/cve-2026-109461-origin-validation-error-in-microsoft-authentication-library-msal)