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CWE-147: Improper Neutralization of Input Terminators

 
Improper Neutralization of Input Terminators
Weakness ID: 147 (Weakness Variant)Status: Draft
+ Description

Description Summary

The software receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could be interpreted as input terminators when they are sent to a downstream component.

Extended Description

For example, a "." in SMTP signifies the end of mail message data, whereas a null character can be used for the end of a string.

+ Time of Introduction
  • Implementation
+ Applicable Platforms

Languages

All

+ Common Consequences
ScopeEffect
Integrity

Technical Impact: Unexpected state

+ Observed Examples
ReferenceDescription
CVE-2000-0319MFV. mail server does not properly identify terminator string to signify end of message, causing corruption, possibly in conjunction with off-by-one error.
CVE-2000-0320MFV. mail server does not properly identify terminator string to signify end of message, causing corruption, possibly in conjunction with off-by-one error.
CVE-2001-0996Mail server does not quote end-of-input terminator if it appears in the middle of a message.
CVE-2002-0001Improperly terminated comment or phrase allows commands.
+ Potential Mitigations

Developers should anticipate that terminators will be injected/removed/manipulated in the input vectors of their software system. Use an appropriate combination of black lists and white lists to ensure only valid, expected and appropriate input is processed by the system.

Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs (i.e., do not rely on a blacklist). A blacklist is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Use and specify a strong output encoding (such as ISO 8859-1 or UTF 8).

Phase: Implementation

Strategy: Input Validation

Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass whitelist validation schemes by introducing dangerous inputs after they have been checked.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class138Improper Neutralization of Special Elements
Development Concepts (primary)699
Research Concepts (primary)1000
CanAlsoBeWeakness BaseWeakness Base170Improper Null Termination
Research Concepts1000
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERInput Terminator
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2008-10-14CWE Content TeamMITREInternal
updated Description
2009-03-10CWE Content TeamMITREInternal
updated Description, Name
2009-07-27CWE Content TeamMITREInternal
updated Potential_Mitigations
2010-04-05CWE Content TeamMITREInternal
updated Description, Name
2011-03-29CWE Content TeamMITREInternal
updated Potential_Mitigations
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2011-06-27CWE Content TeamMITREInternal
updated Common_Consequences
Previous Entry Names
Change DatePrevious Entry Name
2008-01-30Input Terminator
2008-04-11Failure to Remove Input Terminator
2009-03-10Failure to Sanitize Input Terminators
2010-04-05Improper Sanitization of Input Terminators
Page Last Updated: September 12, 2011