CWE WEAKNESSES  /  CWE-807

CWE-807

Reliance on Untrusted Inputs in a Security Decision

What it is

The product uses a protection mechanism that relies on the existence or values of an input, but the input can be modified by an untrusted actor in a way that bypasses the protection mechanism.

Developers may assume that inputs such as cookies, environment variables, and hidden form fields cannot be modified. However, an attacker could change these inputs using customized clients or other attacks. This change might not be detected. When security decisions such as authentication and authorization are made based on the values of these inputs, attackers can bypass the security of the software.Without sufficient encryption, integrity checking, or other mechanism, any input that originates from an outsider cannot be trusted.

Impact

Mitigations

• [Architecture and Design]Store state information and sensitive data on the server side only.Ensure that the system definitively and unambiguously keeps track of its own state and user state and has rules defined for legitimate state transitions. Do not allow any application user to affect state directly in any way other than through legitimate actions leading to state transitions.If information must be stored on t
• [Architecture and Design]Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.With a stateless protocol such as HTTP, use a framework that maintains the state for you.Examples include ASP.NET View State [REF-756] and the OWASP ESAPI Session Management feature [REF-45].Be careful of language features that provide state support
• [Architecture and Design] For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
• [Operation, Implementation] When using PHP, configure the application so that it does not use register_globals. During implementation, develop the application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues.
• [Architecture and Design, Implementation]Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly thro

Real-world CVE examples

• CVE-2009-1549 — Attacker can bypass authentication by setting a cookie to a specific value.
• CVE-2009-1619 — Attacker can bypass authentication and gain admin privileges by setting an "admin" cookie to 1.
• CVE-2009-0864 — Content management system allows admin privileges by setting a "login" cookie to "OK."
• CVE-2008-5784 — e-dating application allows admin privileges by setting the admin cookie to 1.
• CVE-2008-6291 — Web-based email list manager allows attackers to gain admin privileges by setting a login cookie to "admin."

Related weaknesses

Source: MITRE CWE. View on cwe.mitre.org →