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.

Primary

Architecture and Design
COMMISSION: This weakness refers to an incorrect design related to an architectural security tactic.

Implementation

High

Confidentiality
Access Control
Availability
Other
Bypass Protection Mechanism
Gain Privileges or Assume Identity
Varies by Context
Attackers can bypass the security decision to access whatever is being protected. The consequences will depend on the associated functionality, but they can range from granting additional privileges to untrusted users to bypassing important security checks. Ultimately, this weakness may lead to exposure or modification of sensitive data, system crash, or execution of arbitrary code.

Manual Static Analysis
Since this weakness does not typically appear frequently within a single software package, manual white box techniques may be able to provide sufficient code coverage and reduction of false positives if all potentially-vulnerable operations can be assessed within limited time constraints.
High
The effectiveness and speed of manual analysis will be reduced if the there is not a centralized security mechanism, and the security logic is widely distributed throughout the software.

Automated Static Analysis - Binary or Bytecode

According to SOAR [REF-1479], the following detection techniques may be useful:

Cost effective for partial coverage:

Bytecode Weakness Analysis - including disassembler + source code weakness analysis
Binary Weakness Analysis - including disassembler + source code weakness analysis

SOAR Partial

Manual Static Analysis - Binary or Bytecode

According to SOAR [REF-1479], the following detection techniques may be useful:

Cost effective for partial coverage:

Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies

SOAR Partial

Dynamic Analysis with Automated Results Interpretation

According to SOAR [REF-1479], the following detection techniques may be useful:

Cost effective for partial coverage:

Web Application Scanner
Web Services Scanner
Database Scanners

SOAR Partial

Dynamic Analysis with Manual Results Interpretation

According to SOAR [REF-1479], the following detection techniques may be useful:

Cost effective for partial coverage:

Fuzz Tester
Framework-based Fuzzer
Monitored Virtual Environment - run potentially malicious code in sandbox / wrapper / virtual machine, see if it does anything suspicious

SOAR Partial

Manual Static Analysis - Source Code

According to SOAR [REF-1479], the following detection techniques may be useful:

Highly cost effective:

Manual Source Code Review (not inspections)

High

Automated Static Analysis - Source Code

According to SOAR [REF-1479], the following detection techniques may be useful:

Cost effective for partial coverage:

Source code Weakness Analyzer
Context-configured Source Code Weakness Analyzer

SOAR Partial

Architecture or Design Review

According to SOAR [REF-1479], the following detection techniques may be useful:

Highly cost effective:

Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)
Formal Methods / Correct-By-Construction

Cost effective for partial coverage:

Attack Modeling

High

Architecture and Design
Attack Surface Reduction

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 the client, do not do so without encryption and integrity checking, or otherwise having a mechanism on the server side to catch tampering. Use a message authentication code (MAC) algorithm, such as Hash Message Authentication Code (HMAC) [REF-529]. Apply this against the state or sensitive data that has to be exposed, which can guarantee the integrity of the data - i.e., that the data has not been modified. Ensure that a strong hash function is used (CWE-328).

Architecture and Design
Libraries or Frameworks

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, since these might be provided as a convenience to the programmer and may not be considering security.

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
Environment Hardening
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
Attack Surface Reduction

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 through API calls.
Identify all inputs that are used for security decisions and determine if you can modify the design so that you do not have to rely on submitted inputs at all. For example, you may be able to keep critical information about the user's session on the server side instead of recording it within external data.

The following code excerpt reads a value from a browser cookie to determine the role of the user.

Cookie[] cookies = request.getCookies();for (int i =0; i< cookies.length; i++) {Cookie c = cookies[i];if (c.getName().equals("role")) {userRole = c.getValue();}}

The following code could be for a medical records application. It performs authentication by checking if a cookie has been set.

$auth = $_COOKIES['authenticated'];if (! $auth) {if (AuthenticateUser($_POST['user'], $_POST['password']) == "success") {// save the cookie to send out in future responsessetcookie("authenticated", "1", time()+60*60*2);}else {ShowLoginScreen();die("\n");}}DisplayMedicalHistory($_POST['patient_ID']);

The programmer expects that the AuthenticateUser() check will always be applied, and the "authenticated" cookie will only be set when authentication succeeds. The programmer even diligently specifies a 2-hour expiration for the cookie.
However, the attacker can set the "authenticated" cookie to a non-zero value such as 1. As a result, the $auth variable is 1, and the AuthenticateUser() check is not even performed. The attacker has bypassed the authentication.

In the following example, an authentication flag is read from a browser cookie, thus allowing for external control of user state data.

Cookie[] cookies = request.getCookies();for (int i =0; i< cookies.length; i++) {Cookie c = cookies[i];if (c.getName().equals("authenticated") && Boolean.TRUE.equals(c.getValue())) {authenticated = true;}}

The following code samples use a DNS lookup in order to decide whether or not an inbound request is from a trusted host. If an attacker can poison the DNS cache, they can gain trusted status.

struct hostent *hp;struct in_addr myaddr;char* tHost = "trustme.example.com";myaddr.s_addr=inet_addr(ip_addr_string);
hp = gethostbyaddr((char *) &myaddr, sizeof(struct in_addr), AF_INET);if (hp && !strncmp(hp->h_name, tHost, sizeof(tHost))) {trusted = true;} else {trusted = false;}

String ip = request.getRemoteAddr();InetAddress addr = InetAddress.getByName(ip);if (addr.getCanonicalHostName().endsWith("trustme.com")) {trusted = true;}

IPAddress hostIPAddress = IPAddress.Parse(RemoteIpAddress);IPHostEntry hostInfo = Dns.GetHostByAddress(hostIPAddress);if (hostInfo.HostName.EndsWith("trustme.com")) {trusted = true;}

IP addresses are more reliable than DNS names, but they can also be spoofed. Attackers can easily forge the source IP address of the packets they send, but response packets will return to the forged IP address. To see the response packets, the attacker has to sniff the traffic between the victim machine and the forged IP address. In order to accomplish the required sniffing, attackers typically attempt to locate themselves on the same subnet as the victim machine. Attackers may be able to circumvent this requirement by using source routing, but source routing is disabled across much of the Internet today. In summary, IP address verification can be a useful part of an authentication scheme, but it should not be the single factor required for authentication.

CVE-2009-1549
Attacker can bypass authentication by setting a cookie to a specific value.
https://www.cve.org/CVERecord?id=CVE-2009-1549

CVE-2009-1619
Attacker can bypass authentication and gain admin privileges by setting an "admin" cookie to 1.
https://www.cve.org/CVERecord?id=CVE-2009-1619

CVE-2009-0864
Content management system allows admin privileges by setting a "login" cookie to "OK."
https://www.cve.org/CVERecord?id=CVE-2009-0864

CVE-2008-5784
e-dating application allows admin privileges by setting the admin cookie to 1.
https://www.cve.org/CVERecord?id=CVE-2008-5784

CVE-2008-6291
Web-based email list manager allows attackers to gain admin privileges by setting a login cookie to "admin."
https://www.cve.org/CVERecord?id=CVE-2008-6291

SEC09-J
Do not base security checks on untrusted sources

Allowed
This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

CWE Content Team
MITRE
2010-01-18
1.8
2010-02-16

CWE Content Team
MITRE
2010-06-21
updated Common_Consequences, Potential_Mitigations, References

CWE Content Team
MITRE
2010-09-27
updated Potential_Mitigations

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences

CWE Content Team
MITRE
2011-06-27
updated Common_Consequences, Relationships

CWE Content Team
MITRE
2011-09-13
updated Potential_Mitigations, References, Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2012-05-11
updated Demonstrative_Examples, References, Relationships

CWE Content Team
MITRE
2012-10-30
updated Potential_Mitigations

CWE Content Team
MITRE
2013-07-17
updated Relationships

CWE Content Team
MITRE
2014-02-18
updated Potential_Mitigations

CWE Content Team
MITRE
2014-07-30
updated Detection_Factors

CWE Content Team
MITRE
2017-01-19
updated Related_Attack_Patterns

CWE Content Team
MITRE
2017-11-08
updated Likelihood_of_Exploit, Modes_of_Introduction, References, Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2019-01-03
updated Taxonomy_Mappings

CWE Content Team
MITRE
2020-02-24
updated Relationships

CWE Content Team
MITRE
2021-10-28
updated Relationships

CWE Content Team
MITRE
2022-04-28
updated Relationships

CWE Content Team
MITRE
2023-01-31
updated Description

CWE Content Team
MITRE
2023-04-27
updated Potential_Mitigations, References, Relationships

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes, Relationships

CWE Content Team
MITRE
2025-09-09
4.18
2025-09-09
updated Detection_Factors, References

CWE Content Team
MITRE
2025-12-11
4.19
2025-12-11
updated Applicable_Platforms, Relationships, Weakness_Ordinalities