The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes NUL characters or null bytes when they are sent to a downstream component.
As data is parsed, an injected NUL character or null byte may cause the product to believe the input is terminated earlier than it actually is, or otherwise cause the input to be misinterpreted. This could then be used to inject potentially dangerous input that occurs after the null byte or otherwise bypass validation routines and other protection mechanisms.

Primary

Implementation

Integrity
Unexpected State

Developers should anticipate that null characters or null bytes will be injected/removed/manipulated in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system.

Implementation
Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list 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. This 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, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Implementation
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 allowlist validation schemes by introducing dangerous inputs after they have been checked.

CVE-2008-1284
NUL byte in theme name causes directory traversal impact to be worse
https://www.cve.org/CVERecord?id=CVE-2008-1284

CVE-2005-2008
Source code disclosure using trailing null.
https://www.cve.org/CVERecord?id=CVE-2005-2008

CVE-2005-3293
Source code disclosure using trailing null.
https://www.cve.org/CVERecord?id=CVE-2005-3293

CVE-2005-2061
Trailing null allows file include.
https://www.cve.org/CVERecord?id=CVE-2005-2061

CVE-2002-1774
Null character in MIME header allows detection bypass.
https://www.cve.org/CVERecord?id=CVE-2002-1774

CVE-2000-0149
Web server allows remote attackers to view the source code for CGI programs via a null character (%00) at the end of a URL.
https://www.cve.org/CVERecord?id=CVE-2000-0149

CVE-2000-0671
Web server earlier allows allows remote attackers to bypass access restrictions, list directory contents, and read source code by inserting a null character (%00) in the URL.
https://www.cve.org/CVERecord?id=CVE-2000-0671

CVE-2001-0738
Logging system allows an attacker to cause a denial of service (hang) by causing null bytes to be placed in log messages.
https://www.cve.org/CVERecord?id=CVE-2001-0738

CVE-2001-1140
Web server allows source code for executable programs to be read via a null character (%00) at the end of a request.
https://www.cve.org/CVERecord?id=CVE-2001-1140

CVE-2002-1031
Protection mechanism for limiting file access can be bypassed using a null character (%00) at the end of the directory name.
https://www.cve.org/CVERecord?id=CVE-2002-1031

CVE-2002-1025
Application server allows remote attackers to read JSP source code via an encoded null byte in an HTTP GET request, which causes the server to send the .JSP file unparsed.
https://www.cve.org/CVERecord?id=CVE-2002-1025

CVE-2003-0768
XSS 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.
https://www.cve.org/CVERecord?id=CVE-2003-0768

CVE-2004-0189
Decoding function in proxy allows regular expression bypass in ACLs via URLs with null characters.
https://www.cve.org/CVERecord?id=CVE-2004-0189

CVE-2005-3153
Null byte bypasses PHP regexp check (interaction error).
https://www.cve.org/CVERecord?id=CVE-2005-3153

CVE-2005-4155
Null byte bypasses PHP regexp check (interaction error).
https://www.cve.org/CVERecord?id=CVE-2005-4155

Null Character / Null Byte

28
Null Byte Injection

SFP24
Tainted input to command

Allowed
This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

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

PLOVER
2006-07-19
Draft 3
2006-07-19

Eric Dalci
Cigital
2008-07-01
updated Potential_Mitigations

CWE Content Team
MITRE
2008-09-08
updated Relationships, Relationship_Notes, Taxonomy_Mappings

CWE Content Team
MITRE
2008-10-14
updated Description

CWE Content Team
MITRE
2008-11-24
updated Observed_Examples

CWE Content Team
MITRE
2009-07-27
updated Potential_Mitigations

CWE Content Team
MITRE
2010-02-16
updated Taxonomy_Mappings

CWE Content Team
MITRE
2010-04-05
updated Description, Name

CWE Content Team
MITRE
2011-03-29
updated Potential_Mitigations

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences

CWE Content Team
MITRE
2011-06-27
updated Common_Consequences

CWE Content Team
MITRE
2012-05-11
updated Observed_Examples, References, Relationships

CWE Content Team
MITRE
2012-10-30
updated Potential_Mitigations

CWE Content Team
MITRE
2014-07-30
updated Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2017-05-03
updated Potential_Mitigations

CWE Content Team
MITRE
2017-11-08
updated Applicable_Platforms

CWE Content Team
MITRE
2020-02-24
updated Potential_Mitigations, Relationships

CWE Content Team
MITRE
2020-06-25
updated Observed_Examples, Potential_Mitigations

CWE Content Team
MITRE
2023-01-31
updated Description, Potential_Mitigations

CWE Content Team
MITRE
2023-04-27
updated Relationships

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2025-12-11
4.19
2025-12-11
updated Applicable_Platforms, References, Weakness_Ordinalities

Null Character / Null Byte
Failure to Remove Null Character / Null Byte
Failure to Sanitize Null Byte or NUL Character