CVE-2026-45659
CWE-502Published: May 22, 2026· Updated: May 27, 2026
Official Description
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
Technical Analysis
CVE-2026-45659 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 8.8.
CISA has added CVE-2026-45659 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.
From a weakness classification perspective (CWE-502): Insecure deserialization vulnerabilities allow attackers to inject malicious objects during deserialization, potentially enabling remote code execution.
CVSS v3.1 Vector Breakdown
Affected Vendors & Products
Exploit & PoC Resources
Official Patches & Advisories
News & Research Mentioning CVE-2026-45659
CISA says threat actors are exploiting a recently patched SharePoint remote code execution vulnerability (CVE-2026-45659). The post CISA Warns of Actively Exploited Microsoft SharePoint Vulnerability appeared first on SecurityWeek. [xlite_meta score:56 src:SecurityWeek xlite_fp:83dc47b6dd2612ec7c269b72e35da004fdc546816e6a91a3cc9298de85018a65]
The U.S. Cybersecurity and Infrastructure Security Agency (CISA) on Wednesday added a high-severity flaw impacting Microsoft SharePoint Server to its Known Exploited Vulnerabilities (KEV) catalog, citing evidence of active exploitation. The vulnerability, tracked as CVE-2026-45659 (CVSS score: 8.8), is a case of remote code execution arising from the deserialization of untrusted data. The issue [xlite_meta score:53 src:The Hacker News xlite_fp:5437e4e1a6c61b424f62176a994452713ee2683486676db7f709bfd3233e03a9]
CISA has added one new vulnerability to its Known Exploited Vulnerabilities (KEV) Catalog, based on evidence of active exploitation. CVE-2026-45659 Microsoft SharePoint Server Deserialization of Untrusted Data Vulnerability This type of vulnerability is a frequent attack vector for malicious cyber actors and poses significant risks to the federal enterprise. Binding Operational Directive (BOD) 26-04: Prioritizing Security Updates Based on Risk establishes vulnerability management requirements for Federal Civilian Executive Branch (FCEB) agencies. BOD 26-04 reinforces the importance of the KEV Catalog and requires federal agencies to prioritize rapid remediation of high-risk vulnerabilities, specifically those identified by Common Vulnerabilities and [xlite_meta score:48 src:CISA Alerts xlite_fp:04f000fd19726257016a9c4e92241a3e00db8f3c93215299df6ff7e5de6d2542]
Microsoft has rolled out updates to fix a remote code execution vulnerability impacting SharePoint that could be exploited by bad actors in attacks without requiring any specialized conditions to be met. The vulnerability, tracked as CVE-2026-45659, carries a CVSS score of 8.8. It has been assigned an important severity. "Deserialization of untrusted data in Microsoft Office SharePoint allows [xlite_meta score:53 src:The Hacker News xlite_fp:2ddd825787a7b6584380653ad81266949815c8c674b52b5ecde4023a02818439]
All References (1)
Quick Facts
Related CVEs (CWE-502)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2026-45659 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
- !CISA KEV: Federal agencies must patch per BOD 22-01 timeline
- !Active exploitation confirmed — treat as P1