A5: Broken Access Control
App Specific
Exploitation of access control is a core skill of attackers. SAST and DAST tools can detect the absence of access control but cannot verify if it is functional when it is present.
Access control is detectable using manual means, or possibly through automation for the absence of access controls in certain frameworks.
Prevalence
Access control weaknesses are common due to the lack of automated detection, and lack of effective functional testing by application developers. Access control detection is not typically amenable to automated static or dynamic testing.
Manual testing is the best way to detect missing or ineffective access control, including HTTP method (GET vs PUT, etc), controller, direct object references, etc.
Technical
The technical impact is attackers acting as users or administrators, or users using privileged functions, or creating, accessing, updating or deleting every record. The business impact depends on the protection needs of the application and data.
Access control enforces policy such that users cannot act outside of their intended permissions. Failures typically lead to unauthorized information disclosure, modification or destruction of all data, or performing a business function outside of the limits of the user. Common access control vulnerabilities include:
Bypassing access control checks by modifying the URL, internal application state, or the HTML page, or simply using a custom API attack tool.
Allowing the primary key to be changed to another users record, permitting viewing or editing someone else's account.
Elevation of privilege. Acting as a user without being logged in, or acting as an admin when logged in as a user.
Metadata manipulation, such as replaying or tampering with a JSON Web Token (JWT) access control token or a cookie or hidden field manipulated to elevate privileges, or abusing JWT invalidation
CORS misconfiguration allows unauthorized API access.
Force browsing to authenticated pages as an unauthenticated user or to privileged pages as a standard user. Accessing API with missing access controls for POST, PUT and DELETE.
