Failure to Resolve Encoded URI Schemes in a Web Page
Weakness ID: 84 (Weakness Variant)Status: Draft
+ Description

Description Summary

The web application fails to filter user-controlled input for executable script disguised with URI encodings.
+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms



+ Observed Examples
CVE-2005-0563Cross-site scripting (XSS) vulnerability in Microsoft Outlook Web Access (OWA) component in Exchange Server 5.5 allows remote attackers to inject arbitrary web script or HTML via an email message with an encoded javascript: URL ("jav&#X41sc
ript:") in an IMG tag.
CVE-2005-2276Cross-site scripting (XSS) vulnerability in Novell Groupwise WebAccess 6.5 before July 11, 2005 allows remote attackers to inject arbitrary web script or HTML via an e-mail message with an encoded javascript URI (e.g. "j&#X41vascript" in an IMG tag).
CVE-2005-0692Encoded script within BBcode IMG tag.
CVE-2002-0117Encoded "javascript" in IMG tag.
CVE-2002-0118Encoded "javascript" in IMG tag.
+ Potential Mitigations

Resolve all URIs to absolute or canonical representations before processing.

Carefully check each input parameter against a rigorous positive specification (white list) defining the specific characters and format allowed. All input should be sanitized, not just parameters that the user is supposed to specify, but all data in the request, including tag attributes, hidden fields, cookies, headers, the URL itself, and so forth. A common mistake that leads to continuing XSS vulnerabilities is to validate only fields that are expected to be redisplayed by the site. We often encounter data from the request that is reflected by the application server or the application that the development team did not anticipate. Also, a field that is not currently reflected may be used by a future developer. Therefore, validating ALL parts of the HTTP request is recommended.

This involves "HTML Entity Encoding" all non-alphanumeric characters from data that was received from the user and is now being written to the request.

With Struts, you should write all data from form beans with the bean's filter attribute set to true.

Additionally, to help mitigate XSS attacks against the user's session cookie, set the session cookie to be HttpOnly. In browsers that support the HttpOnly feature (such as Internet Explorer), this attribute prevents the user's session cookie from being accessed by client-side scripts, including scripts inserted due to a XSS attack.

+ Weakness Ordinalities
(where the weakness exists independent of other weaknesses)
+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness BaseWeakness Base79Failure to Preserve Web Page Structure ('Cross-site Scripting')
Development Concepts (primary)699
Research Concepts (primary)1000
+ Causal Nature


+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERXSS using Script Via Encoded URI Schemes
+ Related Attack Patterns
CAPEC-IDAttack Pattern Name
(CAPEC Version: 1.4)
32Embedding Scripts in HTTP Query Strings
18Embedding Scripts in Nonscript Elements
+ Content History
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time of Introduction
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Taxonomy Mappings, Weakness Ordinalities
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11XSS using Script Via Encoded URI Schemes