Exploited vulnerabilities / CVE-2026-45659
Confirmed exploited · insecure deserialization · Microsoft SharePoint ServerCVE-2026-45659
Microsoft SharePoint Server insecure deserialization, confirmed exploited in the wild.
Microsoft SharePoint Server contains a deserialization of untrusted data vulnerability which allows an authorized attacker to execute code over a network.
| CISA's name for it | Microsoft SharePoint Server Deserialization of Untrusted Data Vulnerability |
|---|---|
| Vendor and product | Microsoft · SharePoint Server |
| Type | insecure deserialization · CWE-502 |
| Exploited | Confirmed by CISA listed 1 July 2026 |
| Likelihood | one of the most likely to be exploited of every vulnerability tracked |
| Deadline | 4 July 2026 · already passed |
| Used in ransomware | Yes: CISA reports it used in ransomware campaigns |
| Advisories | msrc.microsoft.com ↗ · www.cisa.gov ↗ · www.cisa.gov ↗ · nvd.nist.gov ↗ |
Three steps, in this order
Apply the vendor's fix or mitigation; CISA lists only vulnerabilities seen exploited.
If you cannot patch now, restrict network access to the affected product.
Check for signs of compromise since the date it was added to the list.
| CISA's required action | Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines. |
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Know before someone else finds it
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CVE-2026-45659 in short
Is CVE-2026-45659 being exploited?
Yes. CISA added CVE-2026-45659 to its Known Exploited Vulnerabilities catalogue on 1 July 2026, which it does only on evidence of exploitation in the wild.
What is the CISA deadline for CVE-2026-45659?
US federal agencies must remediate it by 4 July 2026. Everyone else should treat that date as the latest safe point to patch an internet-facing system.
How likely is CVE-2026-45659 to be exploited in the next 30 days?
FIRST's Exploit Prediction Scoring System gives it 80%, the 99th percentile of every CVE it scores.
How do I fix CVE-2026-45659?
Apply the vendor's fix or mitigation; CISA lists only vulnerabilities seen exploited. If you cannot patch now, restrict network access to the affected product. Check for signs of compromise since the date it was added to the list.
Other Microsoft vulnerabilities being exploited
| CVE | Product | Type | Listed |
|---|---|---|---|
| CVE-2026-124194 | Office | exploited vulnerability | 10 November 2026 |
| CVE-2026-96951 | Windows | command injection | 13 October 2026 |
| CVE-2026-65660 | SharePoint | exploited vulnerability | 25 September 2026 |
| CVE-2026-81963 | Windows | privilege escalation | 8 September 2026 |
| CVE-2026-85880 | Windows | privilege escalation | 8 September 2026 |
| CVE-2019-1068 | SQL Server | remote code execution | 26 August 2026 |
Sources: CISA Known Exploited Vulnerabilities catalogue (released 10 November 2026) and FIRST EPSS. Page compiled automatically by SAK T.L.M, the threat-intelligence tool of SAK T.E.C, on 13 November 2026.