Chinese State-Sponsored Hackers Exploit Critical SharePoint Zero-Day

A critical zero-day vulnerability in Microsoft SharePoint servers is being actively weaponized by Chinese state-sponsored hacking groups in a widespread cyberespionage campaign, security researchers have confirmed. The flaw, tracked as CVE-2023-29357, carries a maximum CVSS severity score of 9.8 and enables remote code execution on vulnerable SharePoint systems.

Technical Analysis:
The vulnerability stems from improper input validation in SharePoint's document conversion feature. Attackers can exploit it by sending specially crafted requests to targeted servers, bypassing authentication mechanisms to gain SYSTEM-level privileges. This allows complete server compromise and lateral movement within enterprise networks.

Microsoft acknowledged being aware of the vulnerability since May 2023 but was unable to develop a comprehensive fix before exploits began circulating in June. While the company released a partial mitigation in its July Patch Tuesday updates, security analysts confirm the workaround can be bypassed by determined attackers.

Campaign Details:
The ongoing attacks have compromised approximately 100 organizations across 15 countries, with particular focus on:

• US defense contractors and federal agencies
• German industrial and manufacturing firms
• Southeast Asian government entities

Evidence points to involvement of China-linked APT groups (suspected to be APT40 or APT31) based on:

1. Consistent use of infrastructure previously tied to Chinese operations
2. Deployment of custom malware variants known to these threat actors
3. Targeting patterns aligning with China's strategic intelligence priorities

Impact Assessment:
Successful exploitation allows attackers to:

• Steal sensitive documents and credentials
• Establish persistent backdoors
• Move laterally to other enterprise systems
• Deploy ransomware or wiper malware as secondary payloads

Mitigation Recommendations:

1. Apply Microsoft's temporary workaround (disabling affected SharePoint features)
2. Implement strict network segmentation for SharePoint servers
3. Monitor for anomalous authentication events
4. Conduct forensic analysis for indicators of compromise

Microsoft has not provided an estimated timeline for a complete patch, leaving organizations vulnerable to continued attacks. The incident highlights growing concerns about nation-state exploitation of enterprise collaboration platforms.