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Date: Wed, 5 Sep 2012 13:05:43 -0400 (EDT)
From: cve-assign@...re.org
To: oss-security@...ts.openwall.com
Cc: cve-assign@...re.org
Subject: Re: php header() header injection detection bypass

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>To me, this is what each of the ids represent:
>CVE-2011-1398: describes the protection bypass
>CVE-2012-4388: describes the failure to fully fix the protection bypass 
>(hence the "incomplete fix for CVE-2011-1398")

OK, what seems best at this point is the following:

[revised CVE-2011-1398 description]

  The sapi_header_op function in main/SAPI.c in PHP before 5.3.11 and
  5.4.x before 5.4.0RC2 does not check for %0D sequences (aka carriage
  return characters), which allows remote attackers to bypass an HTTP
  response-splitting protection mechanism via a crafted URL, related
  to improper interaction between the PHP header function and certain
  browsers, as demonstrated by Internet Explorer and Google Chrome.

[new CVE-2012-4388 description]

  The sapi_header_op function in main/SAPI.c in PHP 5.4.0RC2 through
  5.4.0 does not properly determine a pointer during checks for %0D
  sequences (aka carriage return characters), which allows remote
  attackers to bypass an HTTP response-splitting protection mechanism
  via a crafted URL, related to improper interaction between the PHP
  header function and certain browsers, as demonstrated by Internet
  Explorer and Google Chrome. NOTE: this vulnerability exists because
  of an incorrect fix for CVE-2011-1398.


Note 1: We originally thought that there was interest in separate CVE
IDs for "the header function is unsafe when a URL contains any
recognized end-of-line character" and "the header function is unsafe
when a URL contains a %0D sequence." If this were the case, the second
CVE description would mention an "incomplete fix" for the first CVE.
But, we now understand that the first CVE is not wanted at all, which
seems reasonable.

In the actual situation, the
https://bugs.php.net/patch-display.php?bug_id=60227&patch=SAPI.diff&revision=1320563128
patch had a logic flaw related to the "((p = memchr(s, '\n', (e - s)))
|| (p = memchr(s, '\r', (e - s))))" expression. MITRE prefers to
categorize this type of situation as an "incorrect fix" not an
"incomplete fix." Admittedly, for many CVE users it doesn't matter.

The mapping of the two CVEs to a vendor changelog is currently
problematic because http://www.php.net/ChangeLog-5.php has two very
similar references to "Fixed bug #60227" but one of the listed
versions (5.4.0) has the code change with the above-mentioned logic
flaw, whereas the other (5.3.11) has a different code change without
this logic flaw.

Note 2: We probably haven't found the exact affected 5.4.0RC versions,
but this doesn't matter much because those versions aren't widely
used. Specifically, we don't know whether there's a supported download
location for every pre-release version that ever existed, but we
happened to find the http://php.marvel.strk.jp/archive/ directory.
Here, 5.4.0alpha3 (August 2011) does not check for '\r' at all,
whereas 5.4.0RC2 (December 2011) can check for '\r' but has the
above-mentioned logic flaw. This is consistent with the 2011-11-06 SVN
date listed in bug 60227.

- -- 
CVE assignment team, MITRE CVE Numbering Authority
M/S M300
202 Burlington Road, Bedford, MA 01730 USA
[ PGP key available through http://cve.mitre.org/cve/request_id.html ]
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