CVE-2025-53770: Microsoft SharePoint Server RCE Vulnerability

CVE-2025-53770 Overview

Deserialization of untrusted data in on-premises Microsoft SharePoint Server allows an unauthorized attacker to execute code over a network. Microsoft is aware that an exploit for CVE-2025-53770 exists in the wild. Microsoft is preparing and fully testing a comprehensive update to address this vulnerability. In the meantime, please make sure that the mitigation provided in this CVE documentation is in place so that you are protected from exploitation.

Critical Impact
This vulnerability has a critical impact with a CVSS score of 9.8, indicating a high potential for unauthorized code execution and compromise of sensitive information across networked systems.

Affected Products

Microsoft SharePoint Server (*: *: subscription)
Microsoft SharePoint Server 2016 (*: enterprise)
Microsoft SharePoint Server 2019

Discovery Timeline

Not Available - Vulnerability discovered by Not Available
Not Available - Responsible disclosure to microsoft
Not Available - CVE CVE-2025-53770 assigned
Not Available - microsoft releases security patch
2025-07-20 - CVE CVE-2025-53770 published to NVD
2025-10-27 - Last updated in NVD database

Technical Details for CVE-2025-53770

Vulnerability Analysis

This vulnerability arises from insecure deserialization, a common issue where harmful data is deserialized, resulting in unauthorized code execution. Specifically, the vulnerability affects Microsoft SharePoint Server when it processes crafted requests that contain malicious serialized data.

Root Cause

The root cause is deserialization of untrusted data without proper validation and sanitization, leading to execution of arbitrary code.

Attack Vector

The attack vector is network-based, where an attacker can send specially crafted data packets to the vulnerable server.

python

# Example exploitation code (sanitized)
import requests

url = "http://vulnerable-sharepoint-server/site-path"
headers = {
    "Content-Type": "application/octet-stream"
}
serialized_payload = b"
\\x00\\x01\\x02\\x03...\n" # crafted serialized data

response = requests.post(url, data=serialized_payload, headers=headers)
print(response.status_code)

Detection Methods for CVE-2025-53770

Indicators of Compromise

Unusual outbound traffic from SharePoint server
Unauthorized access attempts
Presence of unexpected serialized data patterns

Detection Strategies

Utilizing deep packet inspection (DPI) to identify patterns of serialized data characteristic of known exploits. Integration with threat intelligence services to detect abnormal network behavior is also recommended.

Monitoring Recommendations

Continuously monitor logs for anomalies in user activity and API calls. Implement automated alerts for any deviations indicative of exploitation attempts.

How to Mitigate CVE-2025-53770

Immediate Actions Required

Disable deserialization of untrusted data within SharePoint configurations.
Implement strict network segmentation to limit exposure of SharePoint Server.
Enhance input validation and sanitization measures for all incoming data.

Patch Information

Microsoft is preparing a comprehensive update. Regularly check Microsoft's advisories for the latest patch releases and apply them immediately once available.

Workarounds

Limit functionality related to serialization where possible and use application-level firewalls to block serialization requests.

bash

# Configuration example
echo "<script> Disable deserialization ";
iptables -A INPUT -p tcp --dport 80 -m string --string "serialized-pattern" --algo bm -j DROP

# Logging rule
iptables -A INPUT -j LOG --log-prefix "[Potential Deserializer Attack] "