CVE-2026-88209 — Microsoft Office SharePoint Spoofing Vulnerability
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.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.4% (30-day exploitation probability)+4
- Technical severity (medium)+3
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented patch — msrc.microsoft.com (NIST National Vulnerability Database)
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Microsoft Microsoft SharePoint Server Subscription Edition, Microsoft Sharepoint Server).
- Apply the fixed version or the patch documented under Remediation.
- Exploitation requires user interaction: tighten email/web filtering and warn affected users.
- Search available logs for exploit probes matching the vulnerability class (cross-site scripting), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Microsoft | Microsoft SharePoint Server Subscription Edition | ≥ 16.0.0 and < 16.0.20326.20190 | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Microsoft | Sharepoint Server | < 16.0.20326.20190 | Vulnerable | NIST National Vulnerability Database |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 4.6 | CVSS 3.1 | Medium | 2.1 | 2.5 | secure@microsoft.com via NIST National Vulnerability Database |
| 4.6 | CVSS 3.1 | Medium | — | — | GitHub, Inc. via GitHub Security Advisories |
| 4.6 | CVSS 3.1 | Medium | — | — | microsoft via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N (score shown at the top: secure@microsoft.com) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
- Monitor CSP violation reports and script payloads in reflected parameters.
Timeline
What happened to this CVE, newest first.
- 2026
- Fix documented
- Affected products added · microsoft/sharepoint server
- Source status changed · Awaiting Analysis → Analyzed
- Affected products added · microsoft/microsoft sharepoint server subscription edition
- SSVC assessment updated
- Record published
- CVSS changed · 4.6
- Source status changed · → Awaiting Analysis
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× References added · Oct 14, 2026 – Oct 14, 2026
- 1× Official description updated · Oct 13, 2026 – Oct 13, 2026
References
3 on the record
Elsewhere on this site
Related CVEs (same products)
- High CVE-2026-108452 Microsoft Office SharePoint Remote Code Execution Vulnerability 1h
- High CVE-2026-88164 Microsoft Office SharePoint Elevation of Privilege Vulnerability 1d
- Medium CVE-2026-97783 Microsoft Office SharePoint Spoofing Vulnerability 2d
- Medium CVE-2026-97782 Microsoft Office SharePoint Tampering Vulnerability 2d
- High CVE-2026-97755 Microsoft Office Excel Remote Code Execution Vulnerability 2d
- High CVE-2026-96044 Microsoft Office SharePoint Elevation of Privilege Vulnerability 2d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-88209 is "Microsoft Office SharePoint Spoofing Vulnerability", rated Medium. It affects Microsoft SharePoint Server Subscription Edition (Microsoft); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 4.6 describes technical severity. EPSS 0.36% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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