The posix_mkfifo function in ext/posix/posix.c in PHP before 5.2.12 and 5.3.x before 5.3.1 allows context-dependent attackers to bypass open_basedir restrictions, and create FIFO files, via the pathname and mode arguments, as demonstrated by creating a .htaccess file.
lists.apple.com/archives/security-announce/2010//Mar/msg00001.html
news.php.net/php.announce/79
secunia.com/advisories/37412
secunia.com/advisories/37821
securityreason.com/securityalert/6600
support.apple.com/kb/HT4077
svn.php.net/viewvc/php/php-src/branches/PHP_5_2/ext/posix/posix.c?view=log
svn.php.net/viewvc/php/php-src/branches/PHP_5_3/ext/posix/posix.c?view=log
svn.php.net/viewvc?view=revision&revision=288943
www.mandriva.com/security/advisories?name=MDVSA-2009:285
www.mandriva.com/security/advisories?name=MDVSA-2009:302
www.mandriva.com/security/advisories?name=MDVSA-2009:303
www.openwall.com/lists/oss-security/2009/11/20/2
www.openwall.com/lists/oss-security/2009/11/20/3
www.openwall.com/lists/oss-security/2009/11/20/5
www.php.net/ChangeLog-5.php
www.php.net/releases/5_2_12.php
www.php.net/releases/5_3_1.php
www.vupen.com/english/advisories/2009/3593