SQL Server - access check cache bucket count

In SQL Server, the "access check cache bucket count" configuration option determines the number of buckets used for caching access check information. This cache is used to store access permissions for securables (like tables, views, stored procedures) to avoid repeated access checks, improving query performance by reducing the overhead of permission validation.    

Explanation  

  • When a user or process attempts to access a securable object in SQL Server, the server performs an access check to verify if the user has the necessary permissions to perform the requested operation.  
  • The "access check cache bucket count" setting controls the granularity of caching access check information, with each bucket storing access permissions for specific securable objects.    

Security Risks  

Manipulating the "access check cache bucket count" configuration can impact security in the following ways:    

  1. Cache Invalidation: Setting a low number of cache buckets may result in frequent cache invalidation, leading to increased overhead for access checks and potentially impacting performance.        
  2. Permission Inconsistencies: Inadequate cache bucket count may lead to inconsistent caching of access permissions, potentially allowing unauthorized access to securable objects.        
  3. Cache Poisoning: Insufficient cache buckets can increase the risk of cache poisoning attacks, where malicious users attempt to manipulate the cache to gain unauthorized access.        
  4. Resource Exhaustion: Setting a high number of cache buckets may consume additional memory resources, impacting server performance and potentially leading to resource exhaustion.    

Recommendation

  • It is recommended to configure the "access check cache bucket count" based on the size of the permission cache needed and the frequency of access checks in your SQL Server environment.  
  • Regularly monitor and tune the cache bucket count to balance performance optimization with security requirements.  
  • Implement strong security measures, such as regularly reviewing and auditing permissions, restricting access to securable objects, and following best practices for securing SQL Server to mitigate potential security risks associated with the access check cache.