Trusting HTTP Permission Methods on the Server Side
Weakness ID: 650 (Weakness Variant)Status: Incomplete
+ Description

Description Summary

The server contains a protection mechanism that assumes that any URI that is accessed using HTTP GET will not cause a state change to the associated resource. This might allow attackers to bypass intended access restrictions and conduct resource modification and deletion attacks, since some applications allow GET to modify state.

Extended Description

An application may disallow the HTTP requests to perform DELETE, PUT and POST operations on the resource representation, believing that it will be enough to prevent unintended resource alterations. Even though the HTTP GET specification requires that GET requests should not have side effects, there is nothing in the HTTP protocol itself that prevents the HTTP GET method from performing more than just query of the data. For instance, it is a common practice with REST based Web Services to have HTTP GET requests modifying resources on the server side. Whenever that happens however, the access control needs to be properly enforced in the application. No assumptions should be made that only HTTP DELETE, PUT, and POST methods have the power to alter the representation of the resource being accessed in the request.

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

Languages

All

+ Common Consequences
ScopeEffect
Access Control

Escalation of Privilege

Integrity

Modification of Resources

Confidentiality

Information Disclosure

+ Likelihood of Exploit

High

+ Enabling Factors for Exploitation

The application allows HTTP access to resources.

The application is not properly configured to enforce access controls around the resources accessible via HTTP.

+ Observed Examples
ReferenceDescription
The HTTP GET method is designed to retrieve resources and not to alter the state of the application or resources on the server side. However, developers can easily code programs that accept a HTTP GET request that do in fact create, update or delete data on the server. Both Flickr (http://www.flickr.com/services/api/flickr.photosets.delete.html) and del.icio.us (http://del.icio.us/api/posts/delete) have implemented delete operations using standard HTTP GET requests. These HTTP GET methods do delete data on the server side, despite being called from GET, which is not supposed to alter state.
+ Potential Mitigations

Configure ACLs on the server side to ensure that proper level of access control is defined for each accessible resource representation.

Do not make an assumption that only HTTP PUT, DELETE or POST methods can modify resources, since HTTP GET method may do the same.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory2Environment
Development Concepts (primary)699
ChildOfWeakness ClassWeakness Class227Failure to Fulfill API Contract ('API Abuse')
Research Concepts1000
ChildOfWeakness BaseWeakness Base436Interpretation Conflict
Research Concepts (primary)1000
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
2008-01-30Evgeny LebanidzeCigitalExternal Submission
Modifications
Modification DateModifierOrganizationSource
2008-09-08CWE Content TeamMITREInternal
updated Common Consequences, Relationships
2008-10-14CWE Content TeamMITREInternal
updated Description, Enabling Factors for Exploitation
2009-10-29CWE Content TeamMITREInternal
updated Common Consequences
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