CWE

CWE-158 – Improper Neutralization of Null Byte or NUL Character

Read Time:2 Minute, 12 Second

Description

The software 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 software 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.

Modes of Introduction:

– Implementation

 

 

Related Weaknesses

CWE-138

 

Consequences

Integrity: Unexpected State

 

Potential Mitigations

Phase:

Description: 

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 denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system.

Phase: Implementation

Description: 

Phase: Implementation

Description: 

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 References

  • CVE-2008-1284
    • NUL byte in theme name causes directory traversal impact to be worse
  • CVE-2002-1774
    • Null character in MIME header allows detection bypass.
  • 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.
  • 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.
  • 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.
  • 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.
  • CVE-2002-1031
    • Protection mechanism for limiting file access can be bypassed using a null character (%00) at the end of the directory name.
  • 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.
  • CVE-2003-0768
    • XSS protection mechanism only checks for sequences with an alphabetical character following a (
  • CVE-2004-0189
    • Decoding function in proxy allows regular expression bypass in ACLs via URLs with null characters.
  • CVE-2005-3153
    • Null byte bypasses PHP regexp check (interaction error).
  • CVE-2005-4155
    • Null byte bypasses PHP regexp check (interaction error).