CWE

Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

CWE/SANS Top 25 Most Dangerous Software Errors
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ID

CWE-93: Improper Neutralization of CRLF Sequences ('CRLF Injection')

Weakness ID: 93
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The software uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs.
+ Relationships

The table(s) below shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.

+ Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
+ Relevant to the view "Architectural Concepts" (CWE-1008)
NatureTypeIDName
MemberOfCategoryCategory1019Validate Inputs
+ Relevant to the view "Development Concepts" (CWE-699)
+ Modes Of Introduction

The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the software life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

PhaseNote
Architecture and Design
ImplementationREALIZATION: This weakness is caused during implementation of an architectural security tactic.
+ Applicable Platforms
The listings below show possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.

Languages

(Language-Independent classes): (Undetermined Prevalence)

+ Common Consequences

The table below specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

ScopeImpactLikelihood
Integrity

Technical Impact: Modify Application Data

+ Demonstrative Examples

Example 1

If user input data that eventually makes it to a log message isn't checked for CRLF characters, it may be possible for an attacker to forge entries in a log file.

(bad)
Example Language: Java 
logger.info("User's street address: " + request.getParameter("streetAddress"));
+ Observed Examples
ReferenceDescription
CRLF injection enables spam proxy (add mail headers) using email address or name.
CRLF injection in API function arguments modify headers for outgoing requests.
Spoofed entries in web server log file via carriage returns
Chain: inject fake log entries with fake timestamps using CRLF injection
Chain: Application accepts CRLF in an object ID, allowing HTTP response splitting.
Chain: HTTP response splitting via CRLF in parameter related to URL.
+ Potential Mitigations

Phase: Implementation

Avoid using CRLF as a special sequence.

Phase: Implementation

Appropriately filter or quote CRLF sequences in user-controlled input.
+ Weakness Ordinalities
OrdinalityDescription
Primary
(where the weakness exists independent of other weaknesses)
+ Memberships
This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
+ Notes

Research Gap

Probably under-studied, although gaining more prominence in 2005 as a result of interest in HTTP response splitting.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERCRLF Injection
OWASP Top Ten 2007A2CWE More SpecificInjection Flaws
WASC24HTTP Request Splitting
Software Fault PatternsSFP24Tainted input to command
+ References
[REF-928] Ulf Harnhammar. "CRLF Injection". Bugtraq. 2002-05-07. <http://marc.info/?l=bugtraq&m=102088154213630&w=2>.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVER
Modifications
Modification DateModifierOrganizationSource
2008-07-01Sean EidemillerCigital
added/updated demonstrative examples
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2009-03-10CWE Content TeamMITRE
updated References
2009-05-27CWE Content TeamMITRE
updated Name
2009-10-29CWE Content TeamMITRE
updated Other_Notes
2009-12-28CWE Content TeamMITRE
updated Likelihood_of_Exploit
2010-02-16CWE Content TeamMITRE
updated Related_Attack_Patterns, Taxonomy_Mappings
2010-04-05CWE Content TeamMITRE
updated Related_Attack_Patterns
2010-06-21CWE Content TeamMITRE
updated Description, Name
2011-03-29CWE Content TeamMITRE
updated Description
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated Relationships
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2015-12-07CWE Content TeamMITRE
updated Relationships
2017-11-08CWE Content TeamMITRE
updated Applicable_Platforms, Causal_Nature, Likelihood_of_Exploit, Modes_of_Introduction, References, Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11CRLF Injection
2009-05-27Failure to Sanitize CRLF Sequences (aka 'CRLF Injection')
2010-06-21Failure to Sanitize CRLF Sequences ('CRLF Injection')

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Page Last Updated: November 14, 2017