CVE-2026-64921: Microsoft SharePoint Server Elevation of Privilege Vulnerability
Missing authentication for critical function in Microsoft Office SharePoint allows an authorized attacker to elevate privileges over a network.
CSIRTS triage
- What
- Missing authentication for a critical function in Microsoft SharePoint Server allows authorized attackers to elevate privileges over the network.
- Who is affected
- Authenticated users on networks with affected SharePoint Server deployments can escalate privileges remotely.
- Urgency
- Critical severity (CVSS 8.8) authentication bypass with remote privilege escalation; immediate patching is mandatory.
- Action
- Deploy the SharePoint Server security update for CVE-2026-64921 immediately.
AI-assisted analysis generated from the source advisory — verify against the original.
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Details
Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64921
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-649210.81% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 54% of all EPSS-scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-64921 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
Recent advisories for Microsoft SharePoint Server
A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.
- highCVE-2026-70326: Server-side request forgery (ssrf) in Microsoft Office SharePoint allows an authorized attacke…nvd · 2026-08-11
- highCVE-2026-70324: Server-side request forgery (ssrf) in Microsoft Office SharePoint allows an authorized attacke…nvd · 2026-08-11
- mediumCVE-2026-58639: Server-side request forgery (ssrf) in Microsoft Office SharePoint allows an authorized attacke…nvd · 2026-08-11
- mediumCVE-2026-62839: Microsoft SharePoint Server Spoofing Vulnerabilitymsrc · 2026-08-11
- highCVE-2026-63514: Microsoft SharePoint Server Remote Code Execution Vulnerabilitymsrc · 2026-08-11
- highCVE-2026-65663: Microsoft SharePoint Server Remote Code Execution Vulnerabilitymsrc · 2026-08-11
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