CWE-84 Web页面编码URIScheme转义处理不恰当

Improper Neutralization of Encoded URI Schemes in a Web Page

结构: Simple

Abstraction: Variant

状态: Draft

被利用可能性: unkown

基本描述

The web application improperly neutralizes user-controlled input for executable script disguised with URI encodings.

相关缺陷

• cwe_Nature: ChildOf cwe_CWE_ID: 79 cwe_View_ID: 1000 cwe_Ordinal: Primary

• cwe_Nature: ChildOf cwe_CWE_ID: 79 cwe_View_ID: 699 cwe_Ordinal: Primary

适用平台

Language: {'cwe_Class': 'Language-Independent', 'cwe_Prevalence': 'Undetermined'}

常见的影响

范围	影响	注释
Integrity	Unexpected State

可能的缓解方案

Implementation

策略: Input Validation

Resolve all URIs to absolute or canonical representations before processing.

Implementation

策略: Input Validation

Carefully check each input parameter against a rigorous positive specification (whitelist) defining the specific characters and format allowed. All input should be neutralized, 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.

MIT-30.1 Implementation

策略: Output Encoding

Use and specify an output encoding that can be handled by the downstream component that is reading the output. Common encodings include ISO-8859-1, UTF-7, and UTF-8. When an encoding is not specified, a downstream component may choose a different encoding, either by assuming a default encoding or automatically inferring which encoding is being used, which can be erroneous. When the encodings are inconsistent, the downstream component might treat some character or byte sequences as special, even if they are not special in the original encoding. Attackers might then be able to exploit this discrepancy and conduct injection attacks; they even might be able to bypass protection mechanisms that assume the original encoding is also being used by the downstream component.
The problem of inconsistent output encodings often arises in web pages. If an encoding is not specified in an HTTP header, web browsers often guess about which encoding is being used. This can open up the browser to subtle XSS attacks.

MIT-43 Implementation

策略:

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

MIT-31 Implementation

策略: Attack Surface Reduction

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 more recent versions of Internet Explorer and Firefox), this attribute can prevent the user's session cookie from being accessible to malicious client-side scripts that use document.cookie. This is not a complete solution, since HttpOnly is not supported by all browsers. More importantly, XMLHTTPRequest and other powerful browser technologies provide read access to HTTP headers, including the Set-Cookie header in which the HttpOnly flag is set.

分析过的案例

标识	说明	链接
CVE-2005-0563	Cross-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 ("javAsc ript:") in an IMG tag.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-0563
CVE-2005-2276	Cross-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. "jAvascript" in an IMG tag).	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-2276
CVE-2005-0692	Encoded script within BBcode IMG tag.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-0692
CVE-2002-0117	Encoded "javascript" in IMG tag.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2002-0117
CVE-2002-0118	Encoded "javascript" in IMG tag.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2002-0118

分类映射

映射的分类名	ImNode ID	Fit	Mapped Node Name
PLOVER			XSS using Script Via Encoded URI Schemes
Software Fault Patterns	SFP24		Tainted input to command

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