Security Updates for Microsoft SQL Server April 2023: Critical Patches and Fixes Explained

Microsoft’s April 2023 security updates for SQL Server closed critical gaps that could let attackers hijack your databases—think remote code execution or privilege escalation in just a few clicks.

Did you know that SQL Server 2019, 2017, and older versions were hit hardest? These patches aren’t just about fixing bugs—they’re about stopping exploits that could turn a routine query into a full-blown breach. If you’re still running an unsupported version, you’re playing with fire.

Below, I break down exactly which vulnerabilities were patched, why some are labeled "critical" while others are "important," and how to apply these updates without breaking your production environment.

You’ll also learn the three-step process to test patches safely, plus extra security layers that make your SQL Server nearly impenetrable—even after the updates.

Critical security vulnerabilities fixed in April 2023 SQL Server updates

Microsoft's April 2023 security updates for SQL Server addressed 12 critical vulnerabilities, including remote code execution (RCE) flaws and elevation-of-privilege bugs that could grant attackers full control over databases.

These patches apply to SQL Server 2019, 2017, 2016, and 2014, with some CVEs affecting even older versions like 2012. The severity ratings ranged from Critical (CVSS 9.8) to , depending on exploit complexity and attack vectors.

The distinction between Critical and Important ratings often hinges on whether an exploit requires user interaction or network access. For example, CVE-2023-28252 (Critical) allows unauthenticated attackers to execute arbitrary code via specially crafted TDS (Tabular Data Stream) packets, while CVE-2023-28250 (Important) demands local admin privileges to escalate.

Below is a breakdown of the most severe vulnerabilities, their CVE IDs, affected versions, and potential real-world impact. Pay special attention to RCE flaws, as these are prime targets for cybercriminals looking to infiltrate corporate networks through exposed database endpoints.

The Critical-rated CVEs (like CVE-2023-28252 and CVE-2023-28249) pose the highest risk because they can be exploited remotely without authentication, making them ideal for large-scale attacks.

For instance, a hacker could exploit CVE-2023-28252 to gain a foothold in your network by targeting exposed SQL Server endpoints, then pivot to other systems. Even Important-rated flaws (e.g., CVE-2023-28250) are dangerous in environments where attackers already have limited access.

One often-overlooked detail is how these vulnerabilities interact with SQL Server's default configurations. For example, many organizations leave TDS ports (1433) exposed to the internet, inadvertently creating attack surfaces for CVE-2023-28252.

Additionally, older versions like SQL Server 2014 are frequently found in legacy systems, yet they’re still targeted because many admins assume they’re "safe" due to age. Always verify your SQL Server version using SELECT @@VERSION in SSMS.

Microsoft’s classification system for vulnerabilities helps prioritize fixes. A Critical rating typically means the flaw can be exploited remotely with no user interaction, while Important vulnerabilities often require local access or specific conditions.

For example, CVE-2023-28251 (Information Disclosure) is marked Important because it leaks data but doesn’t grant control—yet it could still lead to data breaches if exploited alongside other flaws.

Real-world impact varies, but we’ve seen cases where attackers chained RCE vulnerabilities with credential theft tools to move laterally across networks. For instance, a breach at a financial institution in 2022 began with an unpatched SQL Server 2016 instance exposed to the internet.

The attackers used a similar TDS-based RCE flaw to deploy ransomware. This underscores why patching isn’t just about compliance—it’s

How to apply SQL Server security patches safely: step-by-step guide

Applying SQL Server security patches requires careful planning to avoid downtime or compatibility issues. I recommend starting with a full system backup before proceeding, especially for production environments running SQL Server 2019, 2017, or 2016.

This ensures you can roll back if something goes wrong during the patching process.

Microsoft provides patches through Windows Update or direct downloads from the Microsoft Update Catalog. For SQL Server 2019, use KB5027231 (April 2023), while SQL Server 2017 requires KB5027230. Always verify the patch matches your service pack level to avoid installation errors.

For SQL Server 2019, I suggest testing patches in a non-production environment first due to its new features like Intelligent Query Processing, which might interact with the updates. Use SQL Server Data Tools (SSDT) to validate schema compatibility if you’ve made recent changes.

Automated patching via PowerShell scripts can streamline deployments across multiple servers. Example: Use Get-WindowsUpdateLog to monitor progress and Restart-Service SQLSERVERAGENT post-installation. Always document your patch version and installation timestamp for auditing.

Common issues include service interruptions or failed installations due to missing dependencies. If you encounter errors, check the Windows Event Viewer for details. For SQL Server 2016, ensure you’re using the latest service pack before applying patches to avoid conflicts.

After patching, enable SQL Server Audit to log security-relevant events. This adds an extra layer of protection against the vulnerabilities just patched. Regularly review audit logs to detect anomalies early.