The product does not neutralize or incorrectly neutralizes web scripting syntax in HTTP headers that can be used by web browser components that can process raw headers, such as Flash.

An attacker may be able to conduct cross-site scripting and other attacks against users who have these components enabled.
If a product does not neutralize user controlled data being placed in the header of an HTTP response coming from the server, the header may contain a script that will get executed in the client's browser context, potentially resulting in a cross site scripting vulnerability or possibly an HTTP response splitting attack. It is important to carefully control data that is being placed both in HTTP response header and in the HTTP response body to ensure that no scripting syntax is present, taking various encodings into account.

Primary

Implementation

High

Integrity
Confidentiality
Availability
Execute Unauthorized Code or Commands
Run arbitrary code.

Confidentiality
Read Application Data
Attackers may be able to obtain sensitive information.

Architecture and Design
Perform output validation in order to filter/escape/encode unsafe data that is being passed from the server in an HTTP response header.

Architecture and Design
Disable script execution functionality in the clients' browser.

In the following Java example, user-controlled data is added to the HTTP headers and returned to the client. Given that the data is not subject to neutralization, a malicious user may be able to inject dangerous scripting tags that will lead to script execution in the client browser.

response.addHeader(HEADER_NAME, untrustedRawInputData);

CVE-2006-3918
Web server does not remove the Expect header from an HTTP request when it is reflected back in an error message, allowing a Flash SWF file to perform XSS attacks.
https://www.cve.org/CVERecord?id=CVE-2006-3918

SFP24
Tainted input to command

Allowed
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.
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.

Evgeny Lebanidze
Cigital
2008-01-30
Draft 8
2008-01-30

Sean Eidemiller
Cigital
2008-07-01
added/updated demonstrative examples

CWE Content Team
MITRE
2008-09-08
updated Common_Consequences, Relationships, Observed_Example

CWE Content Team
MITRE
2008-10-14
updated Description, Name, Observed_Examples, Relationships

CWE Content Team
MITRE
2009-03-10
updated Relationships

CWE Content Team
MITRE
2009-05-27
updated Description, Name

CWE Content Team
MITRE
2009-10-29
updated Common_Consequences

CWE Content Team
MITRE
2010-04-05
updated Description, Name

CWE Content Team
MITRE
2010-06-21
updated Demonstrative_Examples, Description, Observed_Examples

CWE Content Team
MITRE
2010-12-13
updated Common_Consequences

CWE Content Team
MITRE
2011-03-29
updated Description

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences

CWE Content Team
MITRE
2012-05-11
updated Relationships

CWE Content Team
MITRE
2012-10-30
updated Potential_Mitigations

CWE Content Team
MITRE
2014-07-30
updated Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2017-11-08
updated Applicable_Platforms, Enabling_Factors_for_Exploitation

CWE Content Team
MITRE
2020-02-24
updated Applicable_Platforms, Relationships

CWE Content Team
MITRE
2021-10-28
updated Relationships

CWE Content Team
MITRE
2023-01-31
updated Description

CWE Content Team
MITRE
2023-04-27
updated Relationships, Time_of_Introduction

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2025-12-11
4.19
2025-12-11
updated Applicable_Platforms, Relationships, Weakness_Ordinalities

Insufficient Filtering of HTTP Headers for Scripting Syntax
Insufficient Sanitization of HTTP Headers for Scripting Syntax
Improper Sanitization of HTTP Headers for Scripting Syntax