Microsoft SharePoint Server: Cross-site scripting enables spoofing
Summary
A cross-site scripting flaw in the on-premises Microsoft SharePoint Server Subscription Edition (x64) allows spoofing over the network. An attacker needs a valid low-privileged account, and a user must take action, such as opening a crafted page. According to the CVSS vector, the impact is high confidentiality and integrity loss with no availability impact, mainly content spoofing or credential phishing inside SharePoint sites rather than server takeover.
Affected
- Microsoft SharePoint Server Subscription Edition (x64, on-premises), versions 16.0.0 before 16.0.20326.20278
- SharePoint Online (Microsoft 365) is not affected by this on-premises CVE
- Other SharePoint versions, such as SharePoint 2019: Unknown.
Fixed in
- Build 16.0.20326.20278 or later, included in the November 2026 SharePoint security update
- If the farm is at the September 2025 CU, a permissions script must run first, otherwise the SharePoint fixes fail to install
Workaround
- No published workaround. Unknown whether MSRC lists one.
- Install the security update as the primary mitigation.
Exploitation
- No evidence of exploitation in the wild. Microsoft's exploitation index is 'unproven' (E:U).
- Not listed in CISA KEV according to one aggregator; the CISA catalog was not checked directly.
- No public proof-of-concept known.
Our recommendation
- Identify on-premises SharePoint Server Subscription Edition farms and their build numbers.
- Patch in the November 2026 cycle, with priority for farms reachable from the internet or used by external guests.
- Check the September 2025 CU prerequisite before installing.
- Monitor SharePoint sites for unusual content or phishing activity, and enforce multi-factor authentication.
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
- CVE record CVE-2026-111303 www.cve.org
- MSRC security update guide advisory msrc.microsoft.com
- Microsoft update blog (Stefan Gossner), November 2026 SharePoint fixes blog.stefan-gossner.com
- Zero Day Initiative: November 2026 security update review www.zerodayinitiative.com
- Automox: November 2026 Patch Tuesday www.automox.com
- Securityonline: November 2026 Patch Tuesday securityonline.info
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 11 Nov 2026, 06:27.
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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