CWE-472: External Control of Assumed-Immutable Web Parameter

Description

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

Extended Description

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 cookie by the server side application.

ThreatScore

Threat Mapped score: 0.0

Industry: Finiancial

Threat priority: Unclassified

Observed Examples (CVEs)

CVE: CVE-2002-0108

Forum product allows spoofed messages of other users via hidden form fields for name and e-mail address.
CVE: CVE-2000-0253

Shopping cart allows price modification via hidden form field.
CVE: CVE-2000-0254

Shopping cart allows price modification via hidden form field.
CVE: CVE-2000-0926

Shopping cart allows price modification via hidden form field.
CVE: CVE-2000-0101

Shopping cart allows price modification via hidden form field.
CVE: CVE-2000-0102

Shopping cart allows price modification via hidden form field.
CVE: CVE-2000-0758

Allows admin access by modifying value of form field.
CVE: CVE-2002-1880

Read messages by modifying message ID parameter.
CVE: CVE-2000-1234

Send email to arbitrary users by modifying email parameter.
CVE: CVE-2005-1652

Authentication bypass by setting a parameter.
CVE: CVE-2005-1784

Product does not check authorization for configuration change admin script, leading to password theft via modified e-mail address field.
CVE: CVE-2005-2314

Logic error leads to password disclosure.
CVE: CVE-2005-1682

Modification of message number parameter allows attackers to read other people's messages.

Related Attack Patterns (CAPEC)

Attack TTPs

T1539 — Steal Web Session Cookie (credential-access)

Malware

APTs (Intrusion Sets)

Modes of Introduction

Phase	Note
Implementation	OMISSION: This weakness is caused by missing a security tactic during the architecture and design phase.

Common Consequences

Impact: Modify Application Data — Notes: Without appropriate protection mechanisms, the client can easily tamper with cookies and similar web data. Reliance on the cookies without detailed validation can lead to problems such as SQL injection. If you use cookie values for security related decisions on the server side, manipulating the cookies might lead to violations of security policies such as authentication bypassing, user impersonation and privilege escalation. In addition, storing sensitive data in the cookie without appropriate protection can also lead to disclosure of sensitive user data, especially data stored in persistent cookies.

Potential 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 range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright. (N/A)
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. (N/A)

Applicable Platforms

None (Not Language-Specific, Undetermined)

Demonstrative Examples

Intro: In this example, a web application uses the value of a hidden form field (accountID) without having done any input validation because it was assumed to be immutable.

String accountID = request.getParameter("accountID"); User user = getUserFromID(Long.parseLong(accountID));

Intro: Hidden fields should not be trusted as secure parameters.

Body: An attacker can intercept and alter hidden fields in a post to the server as easily as user input fields. An attacker can simply parse the HTML for the substring:

<input type="hidden"

Notes

Relationship: This is a primary weakness for many other weaknesses and functional consequences, including XSS, SQL injection, path disclosure, and file inclusion.
Theoretical: This is a technology-specific MAID problem.

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