CWE WEAKNESSES  /  CWE-472

CWE-472

External Control of Assumed-Immutable Web Parameter

What it is

The web application does not sufficiently verify inputs that are assumed to be immutable but are actually externally controllable, such as hidden form fields.

If a web product does not properly protect assumed-immutable values from modification in hidden form fields, parameters, cookies, or URLs, this can lead to modification of critical data. Web applications often mistakenly make the assumption that data passed to the client in hidden fields or cookies is not susceptible to tampering. Improper validation of data that are user-controllable can lead to the application processing incorrect, and often malicious, input.For example, custom cookies commonly store session data or persistent data across sessions. This kind of session data is normally involved in security related decisions on the server side, such as user authentication and access control. Thus, the cookies might contain sensitive data such as user credentials and privileges. This is a dangerous practice, as it can often lead to improper reliance on the value of the client-provided

Impact

Mitigations

• [Implementation]Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.When performing input validation, consider all potentially relevant properties, including length, type of input, the full r
• [Implementation] Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.

Real-world CVE examples

• CVE-2002-0108 — Forum product allows spoofed messages of other users via hidden form fields for name and e-mail address.
• CVE-2000-0253 — Shopping cart allows price modification via hidden form field.
• CVE-2000-0254 — Shopping cart allows price modification via hidden form field.
• CVE-2000-0926 — Shopping cart allows price modification via hidden form field.
• CVE-2000-0101 — Shopping cart allows price modification via hidden form field.
• CVE-2000-0102 — Shopping cart allows price modification via hidden form field.
• CVE-2000-0758 — Allows admin access by modifying value of form field.
• CVE-2002-1880 — Read messages by modifying message ID parameter.
• CVE-2000-1234 — Send email to arbitrary users by modifying email parameter.
• CVE-2005-1652 — Authentication bypass by setting a parameter.
• CVE-2005-1784 — Product does not check authorization for configuration change admin script, leading to password theft via modified e-mail address field.
• CVE-2005-2314 — Logic error leads to password disclosure.

Related weaknesses

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