Microsoft SharePoint Server: Elevation of privilege due to missing authorization
Summary
A missing authorization check in Microsoft Office SharePoint Server Subscription Edition allows an authenticated attacker with a low-privileged account to elevate privileges over the network. Per the CVSS vector, successful exploitation can impact confidentiality, integrity and availability. The attacker needs a valid login, so the risk is highest for farms reachable from the internet or with many user accounts.
Affected
- Microsoft SharePoint Server Subscription Edition: 16.0.0 to before 16.0.20326.20190 (range from secondary sources, not yet confirmed against Microsoft's product table)
- SharePoint Server 2016 and 2019: Unknown
- Deployment caveat: a third-party blog reports that farms at the September 2025 CU level may need a permission-fix script before the update installs. Unverified.
Fixed in
- KB5002927, build 16.0.20326.20190, released October 13, 2026
Workaround
- No workaround needed when the fix is applied.
- No documented interim mitigation from Microsoft found. Unknown whether one exists.
Exploitation
- Microsoft marks exploit code maturity as unproven (E:U).
- Not listed in CISA KEV according to third-party trackers; not verified directly against the CISA catalogue.
- No public proof of concept found.
- CISA SSVC: exploitation none, automatable no, technical impact total.
Our recommendation
- Confirm whether the farm is SharePoint Server Subscription Edition and check the build number.
- If the build is below 16.0.20326.20190, install KB5002927 after checking the prerequisites in Microsoft's KB article.
- Restrict external exposure of the farm and review accounts with access.
- SharePoint 2016 and 2019 cannot use this fix; plan separately for those systems.
- Monitor for unusual privilege changes or access to sensitive sites.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Microsoft Office SharePoint
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Microsoft Office
- Updates (KB)
- KB5002927
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide msrc.microsoft.com
- Microsoft SharePoint Server Subscription Edition KB 5002927 support.microsoft.com
- Microsoft SharePoint release history learn.microsoft.com
- OpenCVE CVE-2026-88164 app.opencve.io
- Senserva KB 5002927 summary senserva.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 31 Oct 2026, 16:41.
Original description (NVD)
Missing authorization in Microsoft Office SharePoint allows an authorized attacker to elevate privileges over a network.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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