CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')
HTTP agents or components may include a web server, load balancer, reverse proxy, web caching proxy, application firewall, web browser, etc. Regardless of the role, they are expected to maintain coherent, consistent HTTP communication state across all components. However, including unexpected data in an HTTP header allows an attacker to specify the entirety of the HTTP message that is rendered by the client HTTP agent (e.g., web browser) or back-end HTTP agent (e.g., web server), whether the message is part of a request or a response.
When an HTTP request contains unexpected CR and LF characters, the server may respond with an output stream that is interpreted as "splitting" the stream into two different HTTP messages instead of one. CR is carriage return, also given by %0d or \r, and LF is line feed, also given by %0a or \n.
In addition to CR and LF characters, other valid/RFC compliant special characters and unique character encodings can be utilized, such as HT (horizontal tab, also given by %09 or \t) and SP (space, also given as + sign or %20).
These types of unvalidated and unexpected data in HTTP message headers allow an attacker to control the second "split" message to mount attacks such as server-side request forgery, cross-site scripting, and cache poisoning attacks.
HTTP response splitting weaknesses may be present when:
- Data enters a web application through an untrusted source, most frequently an HTTP request.
- The data is included in an HTTP response header sent to a web user without neutralizing malicious characters that can be interpreted as separator characters for headers.
Modes of Introduction
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Implementation |
Applicable Platforms
Type | Class | Name | Prevalence |
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Language | Not Language-Specific | ||
Technology | Web Based |
Relationships
View | Weakness | |||||||
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# ID | View | Status | # ID | Name | Abstraction | Structure | Status | |
CWE-1000 | Research Concepts | Draft | CWE-93 | Improper Neutralization of CRLF Sequences ('CRLF Injection') | Base | Simple | Draft | |
CWE-1000 | Research Concepts | Draft | CWE-79 | Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') | Base | Simple | Stable | |
CWE-700 | Seven Pernicious Kingdoms | Incomplete | CWE-20 | Improper Input Validation | Class | Simple | Stable | |
CWE-1000 | Research Concepts | Draft | CWE-436 | Interpretation Conflict | Class | Simple | Incomplete |
Common Attack Pattern Enumeration and Classification (CAPEC)
The Common Attack Pattern Enumeration and Classification (CAPECâ„¢) effort provides a publicly available catalog of common attack patterns that helps users understand how adversaries exploit weaknesses in applications and other cyber-enabled capabilities.
CAPEC at Mitre.orgCVEs Published
CVSS Severity
CVSS Severity - By Year
CVSS Base Score
# CVE | Description | CVSS | EPSS | EPSS Trend (30 days) | Affected Products | Weaknesses | Security Advisories | Exploits | PoC | Pubblication Date | Modification Date |
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# CVE | Description | CVSS | EPSS | EPSS Trend (30 days) | Affected Products | Weaknesses | Security Advisories | PoC | Pubblication Date | Modification Date |