Attack Chain

1. An unauthenticated attacker sends a specially crafted request to a vulnerable SharePoint server.
2. The request exploits a flaw in the way SharePoint processes specific types of data.
3. This leads to the execution of arbitrary code within the context of the SharePoint application pool.
4. The attacker gains control over the SharePoint server.
5. The attacker leverages the initial access to move laterally within the network.
6. The attacker compromises other systems and resources within the organization’s environment.
7. The attacker installs a webshell for persistent access.
8. The final objective is to exfiltrate sensitive data or deploy ransomware.

Impact

Successful exploitation of CVE-2026-45659 can lead to complete compromise of the SharePoint server and potentially the entire network. An attacker can gain unauthorized access to sensitive data, disrupt services, or deploy malicious payloads like ransomware. Given the widespread use of SharePoint for document management and collaboration, this vulnerability poses a significant risk to organizations across various sectors. If exploited, this vulnerability allows remote code execution, potentially leading to data breaches, system downtime, and financial losses.

Recommendation

• Apply the patches provided in the Microsoft Security Bulletin CVE-2026-45659 to remediate the remote code execution vulnerability on all affected SharePoint servers.
• Deploy the Sigma rule Detect CVE-2026-45659 Exploitation Attempt via HTTP Request to detect potential exploitation attempts.
• Monitor web server logs for suspicious HTTP requests targeting SharePoint servers as described in the Attack Chain.
• Implement network segmentation to limit the potential impact of a successful exploitation as mentioned in the attack chain, specifically lateral movement.