CWE

Null Byte Interaction Error (Poison Null Byte)

ID: 626		Date: (C)2012-05-14   (M)2022-10-10
Type: weakness		Status: DRAFT
Abstraction Type: Variant

Description

The product does not properly handle null bytes or NUL characters when passing data between different representations or components.

Extended Description

A null byte (NUL character) can have different meanings across representations or languages. For example, it is a string terminator in standard C libraries, but Perl and PHP strings do not treat it as a terminator. When two representations are crossed - such as when Perl or PHP invokes underlying C functionality - this can produce an interaction error with unexpected results. Similar issues have been reported for ASP. Other interpreters written in C might also be affected.

Applicable Platforms
Language: PHP
Language: Perl
Language: ASP.NET

Time Of Introduction

• Implementation

Common Consequences

Scope	Technical Impact	Notes
Integrity	Unexpected state

Detection Methods
None

Potential Mitigations

Phase	Strategy	Description	Effectiveness	Notes
Implementation		Remove null bytes from all incoming strings.

Relationships

Related CWE	Type	View	Chain
CWE-626 ChildOf CWE-896	Category	CWE-888

Demonstrative Examples
None

Observed Examples

1. CVE-2005-4155 : NUL byte bypasses PHP regular expression check
2. CVE-2005-3153 : inserting SQL after a NUL byte bypasses whitelist regexp, enabling SQL injection

For more examples, refer to CVE relations in the bottom box.

White Box Definitions
None

Black Box Definitions
None

Taxynomy Mappings
None

References:

1. Rain Forest Puppy .Poison NULL byte. Phrack 55.
2. Brett Moore .0x00 vs ASP file upload scripts.
3. ShAnKaR .ShAnKaR: multiple PHP application poison NULL byte vulnerability.