CWE-87

Improper Neutralization of Alternate XSS Syntax
2006-07-19
00h00 +00:00
Draft
2026-10-28
00h00 +00:00
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名前: Improper Neutralization of Alternate XSS Syntax

The product does not neutralize or incorrectly neutralizes user-controlled input for alternate script syntax.

一般情報

導入モード

Implementation

適用可能なプラットフォーム

言語

クラス: Not Language-Specific (Undetermined)

一般的な結果

スコープ 影響 可能性
Confidentiality
Integrity
Availability
Read Application Data, Execute Unauthorized Code or Commands

観察された例

参考文献 説明

CVE-2002-0738

XSS using "&={script}".

潜在的な緩和策

Phases : Implementation
Resolve all input to absolute or canonical representations before processing.
Phases : Implementation
Carefully check each input parameter against a rigorous positive specification (allowlist) 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.
Phases : Implementation
Phases : Implementation
With Struts, write all data from form beans with the bean's filter attribute set to true.
Phases : Implementation
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.

検出方法

Automated Static Analysis

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

脆弱性マッピングノート

理由 : This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
コメント : 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.

関連する攻撃パターン

CAPEC ID 攻撃パターン名
CAPEC-199 XSS Using Alternate Syntax
An adversary uses alternate forms of keywords or commands that result in the same action as the primary form but which may not be caught by filters. For example, many keywords are processed in a case insensitive manner. If the site's web filtering algorithm does not convert all tags into a consistent case before the comparison with forbidden keywords it is possible to bypass filters (e.g., incomplete black lists) by using an alternate case structure. For example, the "script" tag using the alternate forms of "Script" or "ScRiPt" may bypass filters where "script" is the only form tested. Other variants using different syntax representations are also possible as well as using pollution meta-characters or entities that are eventually ignored by the rendering engine. The attack can result in the execution of otherwise prohibited functionality.

登録情報

名前 組織 日付 リリース日 Version
PLOVER 2006-07-19 +00:00 2006-07-19 +00:00 Draft 3

変更履歴

名前 組織 日付 コメント
Sean Eidemiller Cigital 2008-07-01 +00:00 added/updated demonstrative examples
Eric Dalci Cigital 2008-07-01 +00:00 updated Time_of_Introduction
CWE Content Team MITRE 2008-09-08 +00:00 updated Name, Relationships, Taxonomy_Mappings
CWE Content Team MITRE 2009-07-27 +00:00 updated Related_Attack_Patterns
CWE Content Team MITRE 2010-06-21 +00:00 updated Demonstrative_Examples, Description, Name, Potential_Mitigations
CWE Content Team MITRE 2010-12-13 +00:00 updated Demonstrative_Examples
CWE Content Team MITRE 2011-03-29 +00:00 updated Potential_Mitigations
CWE Content Team MITRE 2011-06-01 +00:00 updated Common_Consequences
CWE Content Team MITRE 2012-05-11 +00:00 updated Relationships
CWE Content Team MITRE 2012-10-30 +00:00 updated Potential_Mitigations
CWE Content Team MITRE 2014-07-30 +00:00 updated Relationships, Taxonomy_Mappings
CWE Content Team MITRE 2017-05-03 +00:00 updated Potential_Mitigations
CWE Content Team MITRE 2017-11-08 +00:00 updated Applicable_Platforms
CWE Content Team MITRE 2020-02-24 +00:00 updated Relationships
CWE Content Team MITRE 2020-06-25 +00:00 updated Potential_Mitigations
CWE Content Team MITRE 2021-03-15 +00:00 updated Demonstrative_Examples
CWE Content Team MITRE 2021-10-28 +00:00 updated Relationships
CWE Content Team MITRE 2023-01-31 +00:00 updated Description
CWE Content Team MITRE 2023-04-27 +00:00 updated Relationships
CWE Content Team MITRE 2023-06-29 +00:00 updated Mapping_Notes
CWE Content Team MITRE 2025-12-11 +00:00 updated Weakness_Ordinalities
CWE Content Team MITRE 2026-10-28 +00:00 updated Detection_Factors