CVE-2020-0618: Microsoft SQL Server SSRS RCE Vulnerability

CVE-2020-0618 Overview

A remote code execution vulnerability exists in Microsoft SQL Server Reporting Services (SSRS) when it incorrectly handles page requests. This vulnerability stems from an insecure deserialization flaw in the ViewState handling mechanism, allowing authenticated attackers to execute arbitrary code on affected SQL Server systems. The vulnerability affects multiple versions of Microsoft SQL Server and has been actively exploited in the wild.

Critical Impact

This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog, indicating confirmed active exploitation. Authenticated attackers can achieve remote code execution on vulnerable SQL Server Reporting Services installations, potentially leading to complete system compromise.

Affected Products

• Microsoft SQL Server 2012 SP4
• Microsoft SQL Server 2014 SP3
• Microsoft SQL Server 2016 SP2 (x64)

Discovery Timeline

• 2020-02-11 - CVE-2020-0618 published to NVD
• 2026-01-13 - Last updated in NVD database

Technical Details for CVE-2020-0618

Vulnerability Analysis

CVE-2020-0618 is an insecure deserialization vulnerability affecting Microsoft SQL Server Reporting Services (SSRS). The flaw exists in how SSRS processes ViewState data within page requests. When SSRS deserializes untrusted ViewState information without proper validation, it creates an opportunity for attackers to inject malicious serialized objects that execute arbitrary code upon deserialization.

The vulnerability requires authentication, meaning an attacker must have valid credentials to access the SSRS web interface. However, once authenticated, exploitation is straightforward and can result in complete compromise of the underlying SQL Server system. The attack can be conducted remotely over the network without requiring user interaction.

Root Cause

The root cause of this vulnerability is CWE-502: Deserialization of Untrusted Data. Microsoft SQL Server Reporting Services fails to properly validate ViewState data before deserializing it. The SSRS web application uses .NET ViewState to maintain state information between page requests. When the application deserializes this ViewState without adequate security controls, an attacker can craft a malicious serialized payload that, when processed, triggers arbitrary code execution on the server.

Attack Vector

The attack vector for CVE-2020-0618 involves network-based exploitation against the SQL Server Reporting Services web interface. An attacker with low-privilege authenticated access to SSRS can craft a specially formatted HTTP request containing a malicious serialized ViewState payload.

The exploitation process typically involves:

1. The attacker authenticates to the SSRS web portal using valid credentials
2. A malicious ViewState payload is constructed containing serialized .NET objects designed to execute code upon deserialization
3. The crafted request is sent to the SSRS server, targeting endpoints that process ViewState data
4. The server deserializes the malicious payload without proper validation
5. The attacker's code executes with the privileges of the SQL Server service account

Public exploits are available through Packet Storm Security, demonstrating the practical exploitability of this vulnerability.

Detection Methods for CVE-2020-0618

Indicators of Compromise

• Unusual HTTP requests to SSRS endpoints containing abnormally large or encoded ViewState parameters
• Unexpected process execution spawned by the SQL Server Reporting Services process (ReportingServicesService.exe)
• Anomalous outbound network connections from the SQL Server hosting SSRS
• Evidence of deserialization gadget chains in web request logs (e.g., ObjectStateFormatter, TypeConfuseDelegate)

Detection Strategies

• Monitor IIS logs for suspicious requests to SSRS URLs containing base64-encoded payloads in ViewState fields
• Implement endpoint detection rules to identify child processes spawned by ReportingServicesService.exe or w3wp.exe serving SSRS
• Deploy network intrusion detection signatures for known .NET deserialization attack patterns
• Review Windows Event Logs for process creation events associated with the SQL Server service account that deviate from baseline behavior

Monitoring Recommendations

• Enable detailed logging on SQL Server Reporting Services and regularly review for anomalous activity
• Configure SIEM alerts for authentication events to SSRS followed by unusual process activity
• Monitor for exploitation attempts using known payload signatures from public exploits
• Implement file integrity monitoring on SSRS installation directories

How to Mitigate CVE-2020-0618

Immediate Actions Required

• Apply the Microsoft security update for CVE-2020-0618 immediately, as this vulnerability is actively exploited
• If patching is not immediately possible, restrict network access to SSRS to trusted IP ranges only
• Review and audit all user accounts with access to SQL Server Reporting Services
• Ensure SQL Server service accounts operate with least-privilege permissions

Patch Information

Microsoft released security updates to address this vulnerability as part of the February 2020 Patch Tuesday. The official security advisory and patch information is available at the Microsoft Security Response Center. Organizations should apply the appropriate cumulative update for their SQL Server version:

• SQL Server 2012 SP4 - Apply the latest security update
• SQL Server 2014 SP3 - Apply the latest security update
• SQL Server 2016 SP2 - Apply the latest security update

Given that this vulnerability is listed in the CISA Known Exploited Vulnerabilities Catalog, federal agencies and critical infrastructure organizations should prioritize remediation.

Workarounds

• Restrict access to SQL Server Reporting Services to only essential personnel and IP addresses using firewall rules
• Implement network segmentation to isolate SSRS servers from untrusted network segments
• If SSRS is not required, consider disabling the Reporting Services feature until patching can be completed
• Deploy web application firewalls (WAF) with rules to detect and block .NET deserialization attacks

# Example: Restrict SSRS access using Windows Firewall
netsh advfirewall firewall add rule name="Block SSRS External" dir=in action=block protocol=tcp localport=80,443 remoteip=any
netsh advfirewall firewall add rule name="Allow SSRS Trusted" dir=in action=allow protocol=tcp localport=80,443 remoteip=10.0.0.0/8