Null Byte Interaction Error (Poison Null Byte)

Opis

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

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.

The poison null byte is frequently useful in path traversal attacks by terminating hard-coded extensions that are added to a filename. It can play a role in regular expression processing in PHP.

Skutki

• Integrity

  Unexpected State

Zapobieganie

• Implementation

  Remove null bytes from all incoming strings.

Przykłady podatności

• CVE-2005-4155 NUL byte bypasses PHP regular expression check
• CVE-2005-3153 inserting SQL after a NUL byte bypasses allowlist regexp, enabling SQL injection

Słabość nadrzędna

• CWE-147 Improper Neutralization of Input Terminators
• CWE-436 Interpretation Conflict

Kiedy powstaje

• Implementation

Dotyczy

PHP, Perl, ASP.NET

Uwagi

Current usage of "poison null byte" is typically related to this C/Perl/PHP interaction error, but the original term in 1998 was applied to an off-by-one buffer overflow involving a null byte.

There are not many CVE examples, because the poison NULL byte is a design limitation, which typically is not included in CVE by itself. It is typically used as a facilitator manipulation to widen the scope of potential attacks against other vulnerabilities.

Źródła

1. Perl CGI problems — Rain Forest Puppy, Phrack, 1999
2. 0x00 vs ASP file upload scripts — Brett Moore
3. ShAnKaR: multiple PHP application poison NULL byte vulnerability — ShAnKaR