CVE-2020-0618: Microsoft SQL Server Reporting Services Remote Code Execution Vulnerability

CVE-2020-0618 is a remote code execution vulnerability in Microsoft SQL Server Reporting Services (SSRS). It stems from unsafe handling of page requests that allows an authenticated attacker to trigger code execution under the Report Server service account. Because SSRS often sits close to business data and runs with elevated privileges relative to ordinary users, successful abuse can give an attacker a foothold for further movement or data access. Specifics of affected builds and exact attack surface must be confirmed against the Microsoft advisory.

Defenders should treat this as a high-priority issue for any environment that exposes SSRS, especially where authentication is reachable from untrusted networks or where the service account has broad database rights. CISA notes that mitigations should be applied per vendor instructions, or the product discontinued if mitigations are unavailable.

How it works

The underlying weakness is CWE-502: deserialization of untrusted data. In this case, SSRS incorrectly processes certain page requests, allowing crafted input to be deserialized in a way that leads to arbitrary code execution. An attacker who already holds valid credentials for the reporting service can send a specially formed request that the Report Server service account then executes. The result is code running with the privileges of that service account rather than the attacker’s own limited identity.

No public exploit mechanics beyond the CISA description are assumed here. In general for this class of flaw, the attacker needs the ability to reach the vulnerable SSRS endpoint and to supply data that the deserialization path will process. Once code execution is achieved, the attacker can typically install further tools, query databases the service account can reach, or establish persistence. Exact request formats and payload requirements are outside the scope of this guidance and must be taken only from the vendor advisory.

Am I affected? How to find it in your systems

Microsoft SQL Server Reporting Services is commonly installed alongside SQL Server instances that provide reporting, dashboards, or scheduled report delivery. It may run on dedicated report servers, on the same host as the database engine, or in multi-server scale-out deployments. Inventory should therefore cover every SQL Server host and any standalone SSRS nodes.

• Enumerate installed SQL Server and SSRS components via inventory tools, Windows features, or the SQL Server Installation Center; note the presence of the Report Server service and its configuration database.
• Identify the version and cumulative update level of SSRS and compare it against the fixed builds listed in the Microsoft security update for CVE-2020-0618. Confirm exact version ranges only from the vendor advisory.
• Check whether the Report Manager or Report Server web endpoints are reachable, and under which authentication modes (Windows, forms, etc.). Note the identity of the Report Server service account and the databases and network resources it can access.
• Review web and application logs for unusual page requests or errors around the reporting endpoints; look for anomalous activity under the service account after successful authentication. Telemetry that shows unexpected process creation or outbound connections from the SSRS process can also be a post-exploitation indicator.

If SSRS is not present, the system is not affected by this particular CVE. If it is present, treat any unpatched instance as potentially vulnerable until the advisory’s version matrix is checked.

How to remediate

The primary remediation is to apply the security update Microsoft released for this vulnerability. Install the appropriate cumulative update or security patch for each affected SSRS instance, following the vendor’s installation and restart guidance. After patching, verify the new build number matches a fixed release listed in the advisory.

• Prioritize internet-facing or broadly authenticated SSRS deployments first, then internal instances that hold sensitive report data.
• Where possible, reduce the privileges of the Report Server service account to the minimum required for report execution and data-source access; this limits the impact of any future similar flaw.
• Ensure SSRS is not exposed beyond the networks that legitimately need it; place it behind authentication gateways and network controls.
• After remediation, re-inventory to confirm no unpatched nodes remain, including scale-out nodes and secondary report servers.

CISA’s required action is to apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable. Discontinuing SSRS is a valid option for organizations that no longer need the reporting capability.

If you can't patch immediately

Until the vendor update can be applied, reduce exposure with compensating controls that address the authenticated deserialization path and the privileges of the service account.

• Segment SSRS so that only authorized management and user networks can reach the Report Server and Report Manager endpoints; block direct access from untrusted or general user segments.
• If a web application firewall or reverse proxy sits in front of SSRS, enable rules that inspect and block anomalous or oversized page-request payloads typical of deserialization attacks; tune carefully to avoid breaking legitimate reports.
• Temporarily disable or restrict features that accept complex page or parameter input if the business can operate without them; confirm impact with report owners first.
• Enforce strong authentication and, where supported, multi-factor authentication for all SSRS access; revoke unused accounts and review membership of roles that can publish or view reports.
• Increase monitoring of the Report Server service account: alert on process creation, unexpected network connections, and changes to report definitions or data sources. Retain logs long enough for forensic review.

These steps do not eliminate the vulnerability; they only lower the likelihood and impact of successful exploitation until the patch is installed.

If your data may have been exposed

Actively exploited remote-code-execution vulnerabilities in reporting services can lead to unauthorized access to the data sources the service account can reach, and potentially to broader compromise of the host. Known ransomware use of this specific CVE is not documented, but any confirmed exploitation should be treated as a possible breach. Review authentication logs, service-account activity, and report-server process behavior for signs of abuse. Organizations that suspect exposure can also run a free exposure scan of their email addresses against known breach data sets to determine whether credentials or personal information have appeared in prior incidents, then force password resets and strengthen monitoring accordingly.