CVE-2026-68775: SQL Server Heap Buffer Overflow RCE

CVE-2026-68775 Overview

CVE-2026-68775 is a heap-based buffer overflow vulnerability in Microsoft SQL Server. The flaw allows an authorized attacker to execute arbitrary code over a network by sending crafted requests to a vulnerable database instance. The weakness is classified as [CWE-122], heap-based buffer overflow, which occurs when a program writes past the bounds of memory allocated on the heap.

An attacker with valid low-privilege database credentials can exploit this issue remotely without user interaction. Successful exploitation compromises confidentiality, integrity, and availability of the SQL Server host. Microsoft published guidance through the Microsoft Security Update Guide CVE-2026-68775.

Critical Impact

An authenticated network attacker can execute arbitrary code in the context of the SQL Server process, leading to full database compromise and potential lateral movement.

Affected Products

• Microsoft SQL Server (see Microsoft Security Update Guide for specific affected builds)

Discovery Timeline

• 2026-09-08 - CVE-2026-68775 published to NVD
• 2026-09-09 - Last updated in NVD database

Technical Details for CVE-2026-68775

Vulnerability Analysis

The vulnerability is a heap-based buffer overflow within SQL Server's request-handling code paths. An authenticated attacker sends a crafted network payload that causes SQL Server to write beyond the boundaries of a heap-allocated buffer. Overwriting adjacent heap metadata or function pointers enables the attacker to redirect execution flow.

Because the vulnerable code runs inside the SQL Server service process, successful exploitation grants code execution with the privileges of that service account. In many deployments the service account holds elevated rights on the local host and network-accessible resources. The attack requires low privileges and no user interaction, which lowers the barrier to reliable exploitation.

The EPSS score is 0.49% as of 2026-09-10, and no public proof-of-concept is currently referenced in the NVD entry.

Root Cause

The root cause is improper validation of the size or length of attacker-controlled input before it is copied into a heap-allocated buffer. This condition matches [CWE-122]. When the copy operation exceeds the allocated region, adjacent memory structures are corrupted, enabling controlled memory writes.

Attack Vector

The attack vector is network-based against the SQL Server TDS listener. The attacker must first authenticate to the SQL Server instance using valid credentials, which can be obtained through credential theft, brute force, or misconfigured accounts. Once authenticated, the attacker submits a malformed request that triggers the overflow.

No verified public exploit code was available at the time of publication. Refer to the Microsoft Security Update Guide CVE-2026-68775 for vendor-supplied technical details.

Detection Methods for CVE-2026-68775

Indicators of Compromise

• Unexpected crashes or restarts of the sqlservr.exe process, particularly with access violation exceptions in the Windows Application event log.
• Spawning of child processes such as cmd.exe, powershell.exe, or rundll32.exe from the SQL Server service account.
• Outbound network connections initiated by sqlservr.exe to untrusted or unusual destinations.

Detection Strategies

• Monitor authentication logs for unusual successful logins to SQL Server instances, especially from atypical source hosts or service accounts.
• Alert on process creation events where sqlservr.exe is the parent process, since legitimate SQL Server workloads rarely spawn interactive shells.
• Inspect memory dumps of crashed SQL Server processes for signs of heap corruption or shellcode.

Monitoring Recommendations

• Enable SQL Server audit logging for logon events and privileged actions, and forward logs to a centralized analytics platform.
• Baseline normal query patterns and flag statistically anomalous requests targeting exposed SQL Server endpoints.
• Track patch state of all SQL Server instances against the fixed builds listed by Microsoft.

How to Mitigate CVE-2026-68775

Immediate Actions Required

• Apply the Microsoft security update for CVE-2026-68775 to all affected SQL Server instances as soon as change windows allow.
• Rotate credentials for accounts with SQL Server login rights, prioritizing service accounts and shared operator accounts.
• Restrict network reachability of SQL Server TDS ports (default 1433/tcp) to trusted application tiers only.

Patch Information

Microsoft has released fixes referenced in the Microsoft Security Update Guide CVE-2026-68775. Administrators should consult the advisory for exact build numbers and cumulative update identifiers that correspond to their SQL Server version.

Workarounds

• Enforce least-privilege database roles so that compromised accounts cannot reach the vulnerable code paths where possible.
• Place SQL Server behind network segmentation and require jump-host access, reducing exposure to attackers who obtain credentials.
• Enable Windows Defender Exploit Guard or equivalent exploit mitigation controls on SQL Server hosts to raise the cost of memory corruption exploitation.

# Restrict SQL Server TDS access to a trusted subnet using Windows Firewall
New-NetFirewallRule -DisplayName "SQL Server 1433 - Trusted Only" \
  -Direction Inbound \
  -Protocol TCP \
  -LocalPort 1433 \
  -RemoteAddress 10.10.20.0/24 \
  -Action Allow

New-NetFirewallRule -DisplayName "SQL Server 1433 - Block Other" \
  -Direction Inbound \
  -Protocol TCP \
  -LocalPort 1433 \
  -Action Block