Failure to Sanitize Null Byte or NUL Character
Weakness ID: 158 (Weakness Variant)Status: Incomplete
+ Description

Description Summary

NUL characters or null bytes injected into an application through input can be used to compromise a system.

Extended Description

As data is parsed, an injected NUL character or null byte may cause the process to take unexpected actions that result in an attack.

+ Time of Introduction
  • Implementation
+ Applicable Platforms



+ Observed Examples
CVE-2005-2008Source code disclosure using trailing null.
CVE-2005-3293Source code disclosure using trailing null.
CVE-2005-2061Trailing null allows file include.
CVE-2002-1774Null character in MIME header allows detection bypass.
CVE-2001-1140web server allows source code for executable programs to be read via a null character (%00) at the end of a request.
CVE-2002-1031Protection mechanism for limiting file access can be bypassed using a null character (%00) at the end of the directory name.
CVE-2003-0768XSS protection mechanism only checks for sequences with an alphabetical character following a (<), so a non-alphabetical or null character (%00) following a < may be processed.
CVE-2004-0189Decoding function in proxy allows regular expression bypass in ACLs via URLs with null characters.
CVE-2005-3153Null byte bypasses PHP regexp check (interaction error).
CVE-2005-4155Null byte bypasses PHP regexp check (interaction error).
+ Potential Mitigations

Developers should anticipate that null characters or null bytes 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: Architecture and Design

Assume all input is malicious. Use a standard input validation mechanism to validate all input for length, type, syntax, and business rules before accepting the data to be displayed or stored. Use an "accept known good" validation strategy.

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

Do not rely exclusively on blacklist validation to detect malicious input or to encode output. There are too many variants to encode a character; you're likely to miss some variants.

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

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class138Improper Sanitization of Special Elements
Development Concepts (primary)699
Research Concepts (primary)1000
+ Relationship Notes

This can be a factor in multiple interpretation errors, other interaction errors, filename equivalence, etc.

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERNull Character / Null Byte
WASC28Null Byte Injection
+ Related Attack Patterns
CAPEC-IDAttack Pattern Name
(CAPEC Version: 1.4)
52Embedding NULL Bytes
53Postfix, Null Terminate, and Backslash
+ Content History
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Potential Mitigations
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Relationship Notes, Taxonomy Mappings
2008-10-14CWE Content TeamMITREInternal
updated Description
2008-11-24CWE Content TeamMITREInternal
updated Observed Examples
2009-07-27CWE Content TeamMITREInternal
updated Potential Mitigations
Previous Entry Names
Change DatePrevious Entry Name
2008-01-30Null Character / Null Byte
2008-04-11Failure to Remove Null Character / Null Byte