Re: function *() php/apache Crash PHP 4.4.2 and 5.1.2 Apr 12 2006 12:29AM
Steven M. Christey (coley mitre org) (2 replies)

Michal Zalewski asked:

>...but how come there's no CVE entry for the bash script in my
>signature?

To which I'll answer the underlying question, i.e. "why assign a CVE
identifier to what appears to be a non-vulnerability?"

1) To clarify: while we changed the CVE naming scheme in October 2005
so that the "CAN" prefix is no longer used, there is still a
conceptual difference between candidates and entries. The number
in the advisory was (and is) a candidate [1]. Any candidate can be
rejected in the future if there is sufficient dispute - along with
a record of the dispute itself.

2) The candidate number was reserved pre-disclosure; the researcher is
responsible for verifying the issue and working with the vendor
before disclosure. SecurityReason can clarify the nature of their
interaction with PHP, and their rationale for publishing this
issue.

3) One does not expect an interpreted language to segfault, and there
have been enough issues in the past couple years in which people
have casually dismissed resource-focused "DoS" attacks that turned
out to be buffer overflows, array index errors, or other memory
corruption problems. This can only be proven with deeper analysis;
the simplicity of an attack is not evidence itself, as your own
research recently highlighted with an obvious attack on script
handlers in IE, which exposed a much more interesting vulnerability
underneath.

4) SecurityReason's advisory does not state the specific impact of the
issue. However, what if the entire Apache server could be caused
to crash? If the server is supporting multiple users, then this is
not just a self-DoS. The vulnerability becomes context-dependent.

5) Interpreted languages could conceivably be held to a higher
security standard than applications written in those languages.
Suppose that this segfault is actually exploitable in some sense.
If a PHP application can be manipulated into making recursive
calls, then it might become exploitable - remotely if the
application happens to be remotely accessible. Recall the the Perl
interpreter format string vulnerability, which is also
context-dependent since it depends on the existence of vulns in
Perl apps to even succeed.

6) The scenarios listed in (3) through (5) might seem unlikely, but
not impossible. Without deeper analysis, we cannot be sure.

- Steve

[1] Note: the distinction between candidates and entries is currently
blurred and under review, since the old process of voting became
too unwieldy due to the growing volume of candidates.

[ reply ]
Re: function *() php/apache Crash PHP 4.4.2 and 5.1.2 Apr 13 2006 06:20PM
Michal Zalewski (lcamtuf dione ids pl)


 

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