Microsoft SharePoint Server: Cross-site scripting enabling spoofing
Summary
Microsoft SharePoint Server Subscription Edition (on-premises) contains a cross-site scripting flaw (CWE-79) in web page generation. An authorized attacker with low privileges can perform spoofing over the network, which requires a victim to interact, for example by clicking a crafted link. The CVSS score of 9.0 is provisional because NVD has not yet analysed the CVE.
Affected
- Microsoft SharePoint Server Subscription Edition (on-premises): 16.0.0 to before 16.0.20326.20278 (per CNA and OffSeq data, to be confirmed on MSRC)
- SharePoint 2019 and 2016: Unknown, check MSRC
Fixed in
- Build 16.0.20326.20278 or later for SharePoint Server Subscription Edition (per OffSeq data, to be confirmed on MSRC)
Workaround
No vendor workaround known. Patching is the stated fix.
Exploitation
- Not known to be exploited in the wild.
- No public proof of concept found; status unknown.
- Not listed in CISA KEV as far as known.
Our recommendation
- Check whether on-premises SharePoint Server Subscription Edition is in use and note the build number.
- Confirm the fixed build on MSRC and apply the update.
- Restrict external access to SharePoint where possible.
- Recheck NVD and MSRC over the next few days, as details may change.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Spoofing – 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 advisory CVE-2026-109454 msrc.microsoft.com
- OffSeq CVE page (version range, exploitation status) radar.offseq.com
- CERT-EU security advisory 2026-009 cert.europa.eu
- Resecurity: July 2026 SharePoint attacks www.resecurity.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, 20:25.
Original description (NVD)
Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Office SharePoint allows an authorized attacker to perform spoofing 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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