Common Vulnerabilities and Exposures assigned an identifier CVE-2010-2094 to
the following vulnerability:

Multiple format string vulnerabilities in the phar extension in PHP
5.3 before 5.3.2 allow context-dependent attackers to obtain sensitive
information (memory contents) and possibly execute arbitrary code via
a crafted phar:// URI that is not properly handled by the (1)
phar_stream_flush, (2) phar_wrapper_unlink, (3) phar_parse_url, or (4)
phar_wrapper_open_url functions in ext/phar/stream.c; and the (5)
phar_wrapper_open_dir function in ext/phar/dirstream.c, which triggers
errors in the php_stream_wrapper_log_error function.

References:
  [1] http://php-security.org/2010/05/14/mops-2010-024-php-phar_stream_flush-format-string-vulnerability/index.html
  [2] http://php-security.org/2010/05/14/mops-2010-025-php-phar_wrapper_open_dir-format-string-vulnerability/index.html
  [3] http://php-security.org/2010/05/14/mops-2010-026-php-phar_wrapper_unlink-format-string-vulnerability/index.html
  [4] http://php-security.org/2010/05/14/mops-2010-027-php-phar_parse_url-format-string-vulnerabilities/index.html
  [5] http://php-security.org/2010/05/14/mops-2010-028-php-phar_wrapper_open_url-format-string-vulnerabilities/index.html

Public PoC (from [1]):

$ php -r "fopen('phar:///usr/bin/phar.phar/*%08x-%08x-%08x-%08x-%08x-%08x-%08x-%08x-%08x','r');"

Credit: All flaws discovered by Stefan Esser.