CVE-2026-45659
Microsoft SharePoint Server
Summary
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
Published: 2026-05-22 · In KEV since: 2026-07-01
Analysis
🔴 Critical — actively exploited
Weakness: Insecure Deserialization (CWE-502). Untrusted serialized data leads to code execution.
How it's exploited: Exploitable over the network (internet-reachable), with low privileges, no user interaction, and with low complexity.
Impact: Full compromise (confidentiality, integrity and availability).
Status: Active exploitation confirmed by CISA (KEV).
- Patch now: it is in CISA's actively-exploited catalog (KEV), with a deadline.
- Reduce exposure: keep it off the internet; firewall, VPN or network segmentation.
- Detect: turn this CVE into detection rules.
MITRE ATT&CK technique: T1190 · Exploit Public-Facing Application · T1059 · Command and Scripting Interpreter
Practice it in the arsenal: WAF Bypass · PowerShell Decoder · Reverse Shells
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
The vector encodes how it's exploited (translated above, in the analysis). Break it down in the CVSS tool →
Sources: CISA KEV · EPSS · FIRST.org · NVD. Analysis derived from the CVSS vector and exploitation status (no AI). Informational; always verify against the vendor's official advisory.