Microsoft SharePoint under ‘active exploitation,’ Homeland Security’s CISA says

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has placed Microsoft SharePoint on its Active Exploitation list, signaling that nation‑state and criminal groups are currently weaponising known vulnerabilities in the platform. The advisory, released in June 2024 and reaffirmed in a July 2024 update, highlights a surge in attacks targeting SharePoint’s web services, authentication mechanisms, and API endpoints.

What “Active Exploitation” Means

When CISA labels a product as under active exploitation, it indicates that threat actors have demonstrated successful, repeatable attacks in the wild. This classification goes beyond a simple “vulnerability disclosed” status; it reflects real‑world compromise, data exfiltration, or ransomware deployment using the identified flaw. For organizations, the warning translates into an urgent need to assess exposure, apply patches, and strengthen detection capabilities.

Key Vulnerabilities Driving the Threat

• CVE‑2024‑21515 – A server‑side request forgery (SSRF) bug in SharePoint’s REST API that allows unauthenticated attackers to reach internal services and harvest credentials.
• CVE‑2024‑31102 – An elevation‑of‑privilege flaw in the SharePoint Designer client, enabling a low‑privilege user to obtain site‑collection administrator rights.
• CVE‑2024‑40809 – A remote code execution (RCE) vulnerability in the SharePoint Search service that can be triggered via crafted search queries.

Threat Actors and Attack Vectors

CISA’s report attributes the exploitation to a blend of state‑affiliated groups—most notably a Chinese cyber‑espionage unit known as “APT31”—and financially motivated ransomware gangs. The typical attack chain starts with a phishing email or a compromised web‑application firewall that delivers a malicious payload to an exposed SharePoint endpoint. Once inside, attackers leverage the SSRF bug to pivot to internal Active Directory (AD) services, harvest Kerberos tickets, and ultimately gain domain‑wide privileges.

Potential Impact on Organizations

SharePoint is often the backbone of document collaboration, intranet portals, and workflow automation. A successful breach can lead to:

• Massive data leakage of intellectual property, HR records, and financial statements.
• Installation of ransomware that encrypts both SharePoint libraries and connected file servers.
• Persistence through malicious web‑parts that survive credential resets.
• Supply‑chain compromise when third‑party apps integrated with SharePoint are tampered with.

Mitigation Recommendations

CISA outlines a layered response strategy:

1. Patch Immediately – Apply Microsoft’s cumulative updates that address the listed CVEs. Verify patch deployment using automated inventory tools.
2. Restrict Access – Enforce Zero‑Trust network segmentation. Limit SharePoint exposure to trusted IP ranges and require multi‑factor authentication (MFA) for all users.
3. Monitor Anomalies – Deploy SIEM rules that flag unusual REST‑API calls, SSRF patterns, or privilege‑escalation attempts. Enable Microsoft Defender for Cloud Apps to surface risky file‑sharing activities.
4. Review Permissions – Conduct a least‑privilege audit of site‑collection admins, external users, and service accounts. Revoke legacy “Full Control” rights where unnecessary.
5. Backup and Recovery – Maintain immutable, offline backups of critical SharePoint libraries. Test restore procedures quarterly to ensure rapid recovery from ransomware incidents.

Long‑Term Defense

Beyond immediate patches, organizations should adopt a proactive security posture for SharePoint:

• Implement Microsoft Secure Score targets specific to collaboration tools.
• Leverage Conditional Access policies that require compliant devices for SharePoint access.
• Regularly scan for misconfigured public‑facing endpoints using tools such as Microsoft Defender Vulnerability Management.
• Engage in threat‑intel sharing through ISACs to stay aware of emerging SharePoint exploits.

Conclusion

The CISA designation of Microsoft SharePoint as under active exploitation underscores the platform’s attractiveness to sophisticated adversaries. Rapid patching, strict access controls, and continuous monitoring are essential to mitigate the immediate risk. By embedding these practices into a broader Zero‑Trust framework, organizations can protect their most valuable collaborative assets and reduce the likelihood of a successful SharePoint‑based breach.