CVE-2026-77483 in SQL Server
Summary
by MITRE • 09/08/2026
Weak authentication in SQL Server allows an authorized attacker to elevate privileges over a network.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 09/09/2026
The vulnerability described involves a critical weakness in the authentication mechanisms of Microsoft SQL Server, specifically allowing for privilege escalation by an authenticated user. This flaw typically stems from improper validation or configuration of security tokens and permissions during the session establishment process. While the attacker is initially granted authorized access to the database engine, often through valid credentials obtained via phishing, credential stuffing, or other initial compromise vectors, they are able to exploit a logic error in how SQL Server processes these authenticated sessions. The core technical flaw lies in the server's failure to strictly enforce role-based access control boundaries when handling specific administrative commands or internal API calls that should be restricted to higher-privilege accounts such as sysadmin members. By crafting specialized requests, an attacker can trick the database engine into executing operations with elevated privileges without requiring additional authentication steps, effectively bypassing the intended security model.
From a technical perspective, this issue aligns closely with CWE-269, which classifies Improper Privilege Management, and specifically relates to conditions where an actor is able to escalate their own permissions beyond what was originally granted by the system administrator. In many instances of such vulnerabilities within SQL Server, the exploitation involves manipulating T-SQL statements or internal RPC calls that do not adequately check if the current session context has sufficient rights for the requested action. The database engine may trust certain metadata or configuration states incorrectly, allowing a low-privileged user to execute commands like sp_addsrvrolemember or modify server-level settings. This represents a significant breakdown in the principle of least privilege, as the system fails to maintain strict isolation between different levels of access within the same instance.
The operational impact of this vulnerability is severe, as it allows an attacker who has already gained foothold on the network and obtained basic database credentials to achieve full control over the SQL Server instance. Once elevated privileges are acquired, the attacker can read, modify, or delete any data stored in all databases hosted by that instance. Furthermore, high-level access often enables lateral movement within the enterprise environment. Attackers may leverage this access to execute operating system commands via extended stored procedures like xp_cmdshell, install malware, create new administrative accounts for persistence, or pivot to other systems connected to the database network. This transforms a relatively contained database compromise into a widespread infrastructure breach, potentially leading to data exfiltration, ransomware deployment, and significant regulatory compliance violations under frameworks such as GDPR or HIPAA depending on the nature of the affected data.
Mitigation strategies must focus on both immediate remediation and long-term architectural hardening. The primary defense is applying the latest security patches released by Microsoft that address these specific authentication logic flaws. Organizations should ensure their SQL Server instances are fully updated to the most recent cumulative update version available for their respective service pack level. Beyond patching, implementing strict network segmentation is crucial; database servers should be isolated in dedicated subnets with firewalls restricting access only to authorized application servers and management workstations. Additionally, enforcing multi-factor authentication for all administrative accounts and using Windows Authentication or Azure Active Directory integration rather than SQL Server Authentication can reduce the risk of credential theft that leads to initial unauthorized access. Regular auditing of server roles and permissions helps ensure no unnecessary elevated privileges are assigned to user accounts, thereby limiting the potential impact if a compromise does occur.