CVEs / CVE-2026-45659
CVE-2026-45659: Microsoft SharePoint Server Deserialization of Untrusted Data Vulnerability
- Known exploited in the CISA KEV catalog since 1 Jul 2026
- high 8.8 CVSS 3.1 (from the CNA)
- EPSS 80.2% chance of exploitation in the next 30 days, higher than 99% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
Microsoft SharePoint Server contains a deserialization of untrusted data vulnerability which allows an authorized attacker to execute code over a network.
Description
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
Affected and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| Microsoft Microsoft SharePoint Enterprise Server 2016 | from 16.0.0, before 16.0.5552.1002 | 16.0.5552.1002 |
| Microsoft Microsoft SharePoint Server 2019 | from 16.0.0, before 16.0.10417.20128 | 16.0.10417.20128 |
| Microsoft Microsoft SharePoint Server Subscription Edition | from 16.0.0, before 16.0.19725.20280 | 16.0.19725.20280 |
Exploitation
| In CISA KEV since | 1 Jul 2026 |
|---|---|
| Due date for US federal agencies | 4 Jul 2026 |
| Used in ransomware campaigns | Known |
| 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. |
Severity
| CVSS 3.1 | 8.8 highCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HScored by the CNA ([email protected]) |
|---|---|
| Weakness | CWE-502 |
References
- CVE-2026-45659 on NVD
- CVE-2026-45659 in the CISA KEV catalog
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45659 (cited by CISA)
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk (cited by CISA)
- https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk (cited by CISA)
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45659 Vendor Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-45659 US Government Resource
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
This product uses data from the NVD API but is not endorsed or certified by the NVD.