VulnerabilityBleeping Computer
9.8 — CRITICAL
Hackers target Microsoft SharePoint RCE chain with PoC exploit
Attackers are now targeting a chain of two Microsoft SharePoint vulnerabilities that can allow them to execute arbitrary code on unpatched servers, according to threat intelligence company Defused. [...]
🤖 AI BriefingAuto-generated threat analysis
🔍Threat Overview
Attackers are targeting a chain of two Microsoft SharePoint vulnerabilities, CVE-2026-55040 and CVE-2026-63520, allowing them to execute arbitrary code on unpatched servers. The first vulnerability is an authentication bypass flaw in the JWT token validation pipeline, while the second is a vulnerability in SharePoint's Business Connectivity Services.
⚙️Technical Details
CVEs
CVE-2026-55040CVE-2026-63520Affected Systems: Microsoft Sharepoint ServerAttack Vectors: NETWORK
Affected Systems
Microsoft Sharepoint Server
Attack Vectors
NETWORK
💥Impact Assessment
Severity: CRITICAL/HIGH
Who Is at Risk
Internet-exposed Microsoft SharePoint servers, including those set up as honeypots.
🛡️Recommended Actions
1Apply the latest security patches to all Microsoft Sharepoint Server instances immediately.
2Restrict access to Microsoft Sharepoint Server to only necessary users and groups.
3Monitor SharePoint Server logs for suspicious activity and implement additional security controls as needed.
📦Affected Products
Microsoft Sharepoint Server
🔐NVD Verified DataVERIFIED
CVE-2026-55040 ↗CVSS 9.1 — CRITICAL
Attack Vector
NETWORK
Complexity
LOW
Vector String
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NWeaknesses
CWE-1390
Affected Products (CPE)
Microsoft Sharepoint Server
CVE-2026-63520 ↗CVSS 8.1 — HIGH
Attack Vector
NETWORK
Complexity
HIGH
Vector String
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:HWeaknesses
CWE-20
Affected Products (CPE)
Microsoft Sharepoint Server
CVE-2026-32201 ↗CVSS 6.5 — MEDIUM
Attack Vector
NETWORK
Complexity
LOW
Vector String
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:NWeaknesses
CWE-20
Affected Products (CPE)
Microsoft Sharepoint Server
CVE-2026-45659 ↗CVSS 8.8 — HIGH
Attack Vector
NETWORK
Complexity
LOW
Vector String
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HWeaknesses
CWE-502
Affected Products (CPE)
Microsoft Sharepoint Server
CVE-2026-56164 ↗CVSS 9.8 — CRITICAL
Attack Vector
NETWORK
Complexity
LOW
Vector String
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HWeaknesses
CWE-306
Affected Products (CPE)
Microsoft Sharepoint Server
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