CVE-2026-65673 Overview
CVE-2026-65673 is a SQL injection vulnerability in Microsoft Entra Connect Sync. The flaw stems from improper neutralization of special elements in SQL commands [CWE-89]. An authenticated attacker with local access can inject crafted SQL statements to elevate privileges on the affected host.
Microsoft Entra Connect Sync bridges on-premises Active Directory with Microsoft Entra ID (formerly Azure AD). Successful exploitation grants an attacker high impact against confidentiality, integrity, and availability of the sync service and its backing database.
Critical Impact
An authorized local attacker can execute arbitrary SQL statements against the Entra Connect Sync database to escalate privileges, potentially compromising directory synchronization between on-premises Active Directory and Microsoft Entra ID.
Affected Products
- Microsoft Entra Connect Sync (refer to the Microsoft CVE-2026-65673 Advisory for specific affected versions)
Discovery Timeline
- 2026-08-11 - CVE-2026-65673 published to NVD
- 2026-08-12 - Last updated in NVD database
Technical Details for CVE-2026-65673
Vulnerability Analysis
The vulnerability resides in how Microsoft Entra Connect Sync constructs SQL statements. User-influenced input reaches the SQL query builder without adequate sanitization or parameterization. An attacker who already holds low-privilege authenticated access on the host running Entra Connect Sync can craft input containing SQL metacharacters to alter query semantics.
Because Entra Connect Sync executes with elevated service permissions to manage directory synchronization, injected SQL runs in a privileged database context. This enables writing to sync metadata, modifying stored credentials, or invoking database functions that yield code execution at higher privilege.
Root Cause
The root cause is improper neutralization of special elements used in SQL commands, classified under [CWE-89]. The affected code path concatenates untrusted input into SQL strings instead of using parameterized queries or stored procedures with bound parameters. This design allows attacker-supplied characters such as single quotes, semicolons, and comment sequences to break out of intended query structure.
Attack Vector
The attack vector is local and requires prior authentication. The attacker must already have valid credentials on the server hosting Entra Connect Sync. User interaction is not required. Exploitation typically involves supplying malicious input to a Sync interface or configuration surface that flows into a vulnerable SQL statement, then using the resulting database privileges to modify sync data or execute commands in the service context.
No public proof-of-concept exploit is available at this time, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. The current EPSS score is 0.799%, placing it in the 53rd percentile for exploitation likelihood.
Refer to the Microsoft CVE-2026-65673 Advisory for detailed technical context.
Detection Methods for CVE-2026-65673
Indicators of Compromise
- Unexpected SQL query patterns in Entra Connect Sync database logs containing metacharacters such as ', --, ;, or xp_ procedures
- Anomalous authentication events or new local accounts created on the Entra Connect Sync server
- Modifications to sync rules, connector configurations, or metadata timestamps outside of scheduled sync windows
- Unexpected child processes spawned by the Entra Connect Sync service account
Detection Strategies
- Enable SQL Server auditing on the ADSync database and alert on queries that deviate from expected sync engine patterns
- Monitor Windows Event Logs on the Sync server for privilege escalation events (Event IDs 4672, 4673, 4688)
- Correlate process execution telemetry from the Sync host against a baseline of legitimate Entra Connect Sync binaries
- Alert on any interactive logon to the Entra Connect Sync server, which should be an infrequent administrative action
Monitoring Recommendations
- Forward Entra Connect Sync host logs and ADSync SQL audit logs to a centralized SIEM for continuous analysis
- Track directory synchronization delta reports for unexpected object changes that may indicate tampering
- Baseline the service account's normal query and process behavior, then alert on deviations
How to Mitigate CVE-2026-65673
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft CVE-2026-65673 Advisory as soon as testing permits
- Restrict interactive and remote logon rights to the Entra Connect Sync server to a minimal set of administrators
- Rotate credentials used by the Entra Connect Sync service and any accounts with local access to the host
- Review recent sync activity and database audit logs for signs of injection attempts or unauthorized changes
Patch Information
Microsoft has published patch guidance at the Microsoft CVE-2026-65673 Advisory. Administrators should consult the advisory for the specific build numbers and update packages that remediate this vulnerability, then deploy through their standard change management process.
Workarounds
- Treat the Entra Connect Sync server as a Tier 0 asset and enforce privileged access workstation (PAW) requirements for administration
- Enable Windows Defender Application Control or AppLocker on the Sync host to restrict which binaries the service account can execute
- Segment the Sync server behind host-based firewall rules that limit local logon sources to jump hosts
- Disable unused local accounts and enforce multi-factor authentication for any account permitted to log on to the host
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
