Unauthenticated user spoofing via capture-replay
Published Sep 8, 2026 · Updated Sep 9, 2026
Authentication bypass in Microsoft Authentication Library for Node.js before 5.6.0 allows remote attackers to spoof users by replaying captured data. Microsoft identifies capture-replay as the mechanism but has not published the affected function, protocol flow, or missing freshness check. Exploitation requires capture of reusable authentication material over a network and grants the victim identity's data access and modification rights without interrupting service.
Summary
What happened
Authentication bypass in Microsoft Authentication Library for Node.js before 5.6.0 allows remote attackers to spoof users by replaying captured data. Microsoft identifies capture-replay as the mechanism but has not published the affected function, protocol flow, or missing freshness check. Exploitation requires capture of reusable authentication material over a network and grants the victim identity's data access and modification rights without interrupting service.
The record
- CVE
- CVE-2026-84003
- Published
- Sep 8, 2026
- Updated
- Sep 9, 2026
- Vendor
- Microsoft
- Product
- Microsoft Authentication Library (MSAL)
- Classifications
- CWE-294, T1550.001
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 8, 2026CVE publishedPublication date reported by the CVE source.
- Sep 9, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=1.0.0 <5.6.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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