Unauthenticated code execution via unverified session tokens
Published Jul 14, 2026 · Updated Jul 14, 2026
Deserialization in Microsoft SharePoint Server 2016, 2019, and Subscription Edition allows remote attackers to execute code over a network. The session-security-token handler accepts tokens without properly verifying their cryptographic signature before processing serialized state. Exploitation requires chaining the forged token with another flaw; resulting code runs as the SharePoint service account without user interaction.
Summary
What happened
Deserialization in Microsoft SharePoint Server 2016, 2019, and Subscription Edition allows remote attackers to execute code over a network. The session-security-token handler accepts tokens without properly verifying their cryptographic signature before processing serialized state. Exploitation requires chaining the forged token with another flaw; resulting code runs as the SharePoint service account without user interaction.
The record
- CVE
- CVE-2026-50522
- Published
- Jul 14, 2026
- Updated
- Jul 14, 2026
- Vendor
- Microsoft Corporation
- Product
- Microsoft SharePoint Enterprise Server 2016
- Classifications
- CWE-502, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 14, 2026CVE publishedPublication date reported by the CVE source.
- Jul 14, 2026Record updatedLatest update available in the CVE record.
- Jul 22, 2026Exploitation reportedMicrosoft SharePoint Deserialization of Untrusted Data Vulnerability
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=16.0.0 <16.0.5561.1001
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
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Activity data is delayed. The latest report is Sep 28, 2026.
View daily counts
| Reporting day | Unique IPs |
|---|---|
| Sep 22, 2026 | Unavailable |
| Sep 23, 2026 | 2 |
| Sep 24, 2026 | 95 |
| Sep 25, 2026 | Unavailable |
| Sep 26, 2026 | Unavailable |
| Sep 27, 2026 | Unavailable |
| Sep 28, 2026 | Unavailable |
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Reported exploitation
- Microsoft SharePoint Deserialization of Untrusted Data Vulnerabilityknown exploited catalog
Technologies
Your stack
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Your stack
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