Improper Access Control (Authorization)
Weakness ID: 285 (Weakness Class)Status: Draft
+ Description

Description Summary

The software does not perform or incorrectly performs access control checks across all potential execution paths.

Extended Description

When access control checks are not applied consistently - or not at all - users are able to access data or perform actions that they should not be allowed to perform. This can lead to a wide range of problems, including information leaks, denial of service, and arbitrary code execution.

+ Alternate Terms

"AuthZ" is typically used as an abbreviation of "authorization" within the web application security community. It is also distinct from "AuthC," which is an abbreviation of "authentication." The use of "Auth" as an abbreviation is discouraged, since it could be used for either authentication or authorization.

+ Time of Introduction
  • Architecture and Design
  • Implementation
  • Operation
+ Applicable Platforms



Technology Classes

Web-Server: (Often)

Database-Server: (Often)

+ Modes of Introduction

A developer may introduce authorization weaknesses because of a lack of understanding about the underlying technologies. For example, a developer may assume that attackers cannot modify certain inputs such as headers or cookies.

Authorization weaknesses may arise when a single-user application is ported to a multi-user environment.

+ Common Consequences

An attacker could read sensitive data, either by reading the data directly from a data store that is not properly restricted, or by accessing insufficiently-protected, privileged functionality to read the data.


An attacker could modify sensitive data, either by writing the data directly to a data store that is not properly restricted, or by accessing insufficiently-protected, privileged functionality to write the data.


An attacker could gain privileges by modifying or reading critical data directly, or by accessing insufficiently-protected, privileged functionality.

+ Likelihood of Exploit


+ Detection Methods

Automated Static Analysis

Automated static analysis is useful for detecting commonly-used idioms for authorization. A tool may be able to analyze related configuration files, such as .htaccess in Apache web servers, or detect the usage of commonly-used authorization libraries.

Generally, automated static analysis tools have difficulty detecting custom authorization schemes. In addition, the software's design may include some functionality that is accessible to any user and does not require an authorization check; an automated technique that detects the absence of authorization may report false positives.

Effectiveness: Limited

Automated Dynamic Analysis

Automated dynamic analysis may find many or all possible interfaces that do not require authorization, but manual analysis is required to determine if the lack of authorization violates business logic

Manual Analysis

This weakness can be detected using tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session.

Specifically, manual static analysis is useful for evaluating the correctness of custom authorization mechanisms.

Effectiveness: Moderate

These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules. However, manual efforts might not achieve desired code coverage within limited time constraints.

+ Demonstrative Examples

Example 1

The following program could be part of a bulletin board system that allows users to send private messages to each other. This program intends to authenticate the user before deciding whether a private message should be displayed. Assume that LookupMessageObject() ensures that the $id argument is numeric, constructs a filename based on that id, and reads the message details from that file. Also assume that the program stores all private messages for all users in the same directory.

(Bad Code)
Example Language: PerlĀ 
sub DisplayPrivateMessage {
my($id) = @_;
my $Message = LookupMessageObject($id);
print "From: " . encodeHTML($Message->{from}) . "<br>\n";
print "Subject: " . encodeHTML($Message->{subject}) . "\n";
print "<hr>\n";
print "Body: " . encodeHTML($Message->{body}) . "\n";

my $q = new CGI;
# For purposes of this example, assume that CWE-309 and
# CWE-523 do not apply.
if (! AuthenticateUser($q->param('username'), $q->param('password'))) {
ExitError("invalid username or password");

my $id = $q->param('id');

While the program properly exits if authentication fails, it does not ensure that the message is addressed to the user. As a result, an authenticated attacker could provide any arbitrary identifier and read private messages that were intended for other users.

One way to avoid this problem would be to ensure that the "to" field in the message object matches the username of the authenticated user.

+ Observed Examples
CVE-2009-3168Web application does not restrict access to admin scripts, allowing authenticated users to reset administrative passwords.
CVE-2009-2960Web application does not restrict access to admin scripts, allowing authenticated users to modify passwords of other users.
CVE-2009-3597Web application stores database file under the web root with insufficient access control (CWE-219), allowing direct request.
CVE-2009-2282Terminal server does not check authorization for guest access.
CVE-2009-3230Database server does not use appropriate privileges for certain sensitive operations.
CVE-2009-2213Gateway uses default "Allow" configuration for its authorization settings.
CVE-2009-0034Chain: product does not properly interpret a configuration option for a system group, allowing users to gain privileges.
CVE-2008-6123Chain: SNMP product does not properly parse a configuration option for which hosts are allowed to connect, allowing unauthorized IP addresses to connect.
CVE-2008-5027System monitoring software allows users to bypass authorization by creating custom forms.
CVE-2008-7109Chain: reliance on client-side security (CWE-602) allows attackers to bypass authorization using a custom client.
CVE-2008-3424Chain: product does not properly handle wildcards in an authorization policy list, allowing unintended access.
CVE-2009-3781Content management system does not check access permissions for private files, allowing others to view those files.
CVE-2008-4577ACL-based protection mechanism treats negative access rights as if they are positive, allowing bypass of intended restrictions.
CVE-2008-6548Product does not check the ACL of a page accessed using an "include" directive, allowing attackers to read unauthorized files.
CVE-2007-2925Default ACL list for a DNS server does not set certain ACLs, allowing unauthorized DNS queries.
CVE-2006-6679Product relies on the X-Forwarded-For HTTP header for authorization, allowing unintended access by spoofing the header.
CVE-2005-3623OS kernel does not check for a certain privilege before setting ACLs for files.
CVE-2005-2801Chain: file-system code performs an incorrect comparison (CWE-697), preventing defauls ACLs from being properly applied.
CVE-2001-1155Chain: product does not properly check the result of a reverse DNS lookup because of operator precedence (CWE-783), allowing bypass of DNS-based access restrictions.
+ Potential Mitigations

Phase: Architecture and Design

Divide your application into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries.

Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.

Phase: Architecture and Design

Ensure that you perform access control checks related to your business logic. These checks may be different than the access control checks that you apply to more generic resources such as files, connections, processes, memory, and database records. For example, a database may restrict access for medical records to a specific database user, but each record might only be intended to be accessible to the patient and the patient's doctor.

Phase: Architecture and Design

Use authorization frameworks such as the JAAS Authorization Framework and the OWASP ESAPI Access Control feature.

Phase: Architecture and Design

For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page.

One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.

Phases: System Configuration; Installation

Use the access control capabilities of your operating system and server environment and define your access control lists accordingly. Use a "default deny" policy when defining these ACLs.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory254Security Features
Seven Pernicious Kingdoms (primary)700
ChildOfWeakness ClassWeakness Class284Access Control (Authorization) Issues
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory721OWASP Top Ten 2007 Category A10 - Failure to Restrict URL Access
Weaknesses in OWASP Top Ten (2007) (primary)629
ChildOfCategoryCategory723OWASP Top Ten 2004 Category A2 - Broken Access Control
Weaknesses in OWASP Top Ten (2004) (primary)711
ChildOfCategoryCategory7532009 Top 25 - Porous Defenses
Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors (primary)750
ChildOfCategoryCategory8032010 Top 25 - Porous Defenses
Weaknesses in the 2010 CWE/SANS Top 25 Most Dangerous Programming Errors (primary)800
ParentOfWeakness VariantWeakness Variant219Sensitive Data Under Web Root
Research Concepts (primary)1000
ParentOfWeakness BaseWeakness Base551Incorrect Behavior Order: Authorization Before Parsing and Canonicalization
Development Concepts (primary)699
Research Concepts1000
ParentOfWeakness ClassWeakness Class638Failure to Use Complete Mediation
Research Concepts1000
ParentOfWeakness BaseWeakness Base804Guessable CAPTCHA
Development Concepts (primary)699
Research Concepts (primary)1000
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
7 Pernicious KingdomsMissing Access Control
OWASP Top Ten 2007A10CWE More SpecificFailure to Restrict URL Access
OWASP Top Ten 2004A2CWE More SpecificBroken Access Control
+ Related Attack Patterns
CAPEC-IDAttack Pattern Name
(CAPEC Version: 1.4)
1Accessing Functionality Not Properly Constrained by ACLs
13Subverting Environment Variable Values
17Accessing, Modifying or Executing Executable Files
87Forceful Browsing
39Manipulating Opaque Client-based Data Tokens
45Buffer Overflow via Symbolic Links
51Poison Web Service Registry
59Session Credential Falsification through Prediction
60Reusing Session IDs (aka Session Replay)
77Manipulating User-Controlled Variables
76Manipulating Input to File System Calls
104Cross Zone Scripting
+ References
NIST. "Role Based Access Control and Role Based Security". <>.
[REF-11] M. Howard and D. LeBlanc. "Writing Secure Code". Chapter 4, "Authorization" Page 114; Chapter 6, "Determining Appropriate Access Control" Page 171. 2nd Edition. Microsoft. 2002.
+ Content History
Submission DateSubmitterOrganizationSource
7 Pernicious KingdomsExternally Mined
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time of Introduction
Suggested OWASP Top Ten 2004 mapping
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Other Notes, Taxonomy Mappings
2009-01-12CWE Content TeamMITREInternal
updated Common Consequences, Description, Likelihood of Exploit, Name, Other Notes, Potential Mitigations, References, Relationships
2009-03-10CWE Content TeamMITREInternal
updated Potential Mitigations
2009-05-27CWE Content TeamMITREInternal
updated Description, Related Attack Patterns
2009-07-27CWE Content TeamMITREInternal
updated Relationships
2009-10-29CWE Content TeamMITREInternal
updated Type
2009-12-28CWE Content TeamMITREInternal
updated Applicable Platforms, Common Consequences, Demonstrative Examples, Detection Factors, Modes of Introduction, Observed Examples, Relationships
Previous Entry Names
Change DatePrevious Entry Name
2009-01-12Missing or Inconsistent Access Control