CVE-2026-66808: Microsoft SharePoint Server Remote Code Execution Vulnerability
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
CSIRTS triage
- What
- Unsafe deserialization of untrusted data in Microsoft SharePoint Server allows remote code execution by an authorized attacker.
- Who is affected
- Deployments of Microsoft SharePoint Server with authenticated access.
- Urgency
- Critical severity (CVSS 8.8) with network-accessible code execution; immediate patching required.
- Action
- Apply the latest security patch for Microsoft SharePoint Server from Microsoft Update 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-2026-66808
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.
- Moderate exploitation riskCVE-2026-668081.6% 30-day exploitation probability. Patch within normal cadence, watch for KEV listing. Riskier than 73% of all EPSS-scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-66808 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
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