Microsoft SharePoint Server: Remote code execution via deserialization
Summary
Deserialization of untrusted data in Microsoft SharePoint Server Subscription Edition allows an authorized attacker to execute code over the network. The attacker needs a valid low-privilege account, so staff accounts or compromised credentials are enough. Successful exploitation could fully compromise confidentiality, integrity and availability (CVSS 8.8). At the time of research, no exploitation and no public proof of concept were known for this CVE.
Affected
- SharePoint Server Subscription Edition: 16.0.0 before 16.0.20326.20278
- Unconfirmed: whether SharePoint Server 2019 or 2016 are affected. Check the MSRC advisory for the full product list.
Fixed in
- Build 16.0.20326.20278 (November 2026 CU, Subscription Edition)
- Security update KB 5002945
- Installation warning: farms on the September 2025 CU may need a folder-permission correction first, otherwise the install fails. The blog post by Stefan Gossner names a PowerShell fix script.
Workaround
- None documented for this CVE. Patching is the fix.
- General CISA SharePoint hardening (not specific to this CVE): do not expose SharePoint Servers directly to the internet, block external access to Central Administration, and enable AMSI with request body scanning where feasible.
Exploitation
- Exploited in the wild: no evidence found for this CVE. Microsoft's CVSS vector marks exploit maturity as Unproven (E:U).
- Public proof of concept: none found.
- Related CVEs are being exploited: CVE-2026-45659 (deserialization RCE) was added to the CISA KEV catalog in July 2026. This does not change the status of CVE-2026-110044 but shows the same bug family is actively targeted.
Our recommendation
- Check whether your SharePoint build is below 16.0.20326.20278.
- Install KB 5002945 or the November 2026 CU, and check the farm's patch level first.
- If the server is reachable from the internet, restrict access now.
- Monitor logs for unusual deserialization errors and unexpected process starts on SharePoint servers.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Remote code execution – Microsoft Office SharePoint
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Microsoft Office
- Updates (KB)
- KB5002945
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Response Center: CVE-2026-110044 msrc.microsoft.com
- CVE.org record CVE-2026-110044 www.cve.org
- Stefan Gossner: SharePoint security fixes with November 2026 PU blog.stefan-gossner.com
- Stefan Gossner: November 2026 CU for SharePoint Server Subscription Edition blog.stefan-gossner.com
- Strix AI: CVE-2026-110044 www.strix.ai
- CISA: SharePoint hardening after new exploitations www.cisa.gov
- SecurityWeek: CISA warns of actively exploited SharePoint vulnerability www.securityweek.com
- Zero Day Initiative: ZDI-26-412 www.zerodayinitiative.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 10 Nov 2026, 23:51.
Original description (NVD)
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code 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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