Microsoft Office SharePoint: Remote code execution through deserialization
Summary
A deserialization flaw in Microsoft Office SharePoint lets an authorized attacker run code on the server over the network. According to the CNA data, only SharePoint Server Subscription Edition is listed as affected. The CVSS vector requires low privileges and no user interaction, so a compromised user account is enough to attempt the attack.
Affected
- Microsoft SharePoint Server Subscription Edition, versions 16.0.0 to below 16.0.20326.20278 (per CNA data; upper bound not yet verified against the MSRC advisory)
- Other SharePoint versions: Unknown.
Fixed in
- November 2026 security update for SharePoint Server Subscription Edition (KB 5002945, identical to the November 2026 CU according to the vendor blog)
- Exact fixed build: Unknown, verify in the MSRC advisory.
Workaround
- No CVE-specific workaround known. Install the security update.
- Pre-installation check: if the farm is at the September 2025 CU, a PowerShell script must first correct folder permissions. Read the script before running it.
Exploitation
- Not listed in the CISA KEV catalog at the time of the sources.
- No public proof of concept or exploitation reports found.
- CISA SSVC: exploitation none, not automatable, total technical impact.
Our recommendation
- Check whether any SharePoint farm runs Subscription Edition and which build it is on.
- Read the MSRC advisory for the exact fixed builds and KB number.
- Handle the permission fix first if the farm is on the September 2025 CU.
- Patch in the next maintenance window and check whether SharePoint is reachable from the internet; prioritize externally published servers.
- Review SharePoint logs for unexpected deserialization errors or unusual process execution.
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 Update Guide (CVE-2026-109464) msrc.microsoft.com
- Stefan Gossner: SharePoint security fixes November 2026 blog.stefan-gossner.com
- GitHub CVE alert CVE-2026-109464 github.com
- Strix: CVE-2026-109464 www.strix.ai
- CISA: SharePoint hardening after new exploitations (July 2026) 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, 23:57.
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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