Microsoft SharePoint Server: Elevation of privilege due to incorrect authorization
Summary
Microsoft SharePoint Server Subscription Edition (on-premises) contains an incorrect authorization flaw (CWE-863). An attacker with a valid low-privilege account can reach the server over the network and gain higher privileges, which may affect confidentiality, integrity and availability. No user interaction is needed, but the attacker must already have an account.
Affected
- Microsoft SharePoint Server Subscription Edition: 16.0.0 to before 16.0.20326.20136
- SharePoint 2019 and SharePoint 2016: Unknown (not listed in the CVE record)
Fixed in
- Build 16.0.20326.20136 or later (implied by the CVE record; verify on the MSRC advisory)
Workaround
Unknown. No workaround is documented; apply the update.
Exploitation
- No known exploitation of this CVE as of publication
- The CVE record marks exploit maturity as unproven
- No public proof of concept found
- Not in the CISA KEV catalog as of publication (per aggregator data)
Our recommendation
- Confirm whether SharePoint Server Subscription Edition is in use and which build is installed
- Read the MSRC advisory for exact fixed builds and the status of SharePoint 2019 and 2016
- Install the fixed build or a later cumulative update as soon as possible
- Review accounts with SharePoint access, especially external and guest accounts
- Do not expose SharePoint Server directly to the internet
- Monitor SharePoint logs for unusual privilege changes
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Microsoft Office SharePoint
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation unlikely
- Product family
- Microsoft Office
- Updates (KB)
- KB5002908
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Response Center: CVE-2026-123391 msrc.microsoft.com
- CVE Record CVE-2026-123391 www.cve.org
- Strix: CVE-2026-123391 www.strix.ai
- CISA: Urges SharePoint hardening after new exploitations www.cisa.gov
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 10 Nov 2026, 21:11.
Original description (NVD)
Incorrect 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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