The strip_tags function in PHP 4.x up to 4.3.7, and 5.x up to 5.0.0RC3, does not filter null (\0) characters within tag names when restricting input to allowed tags, which allows dangerous tags to be processed by web browsers such as Internet Explorer and Safari, which ignore null characters and facilitate the exploitation of cross-site scripting (XSS) vulnerabilities.

The IMAP functionality in PHP before 4.3.1 allows remote attackers to cause a denial of service via an e-mail message with a (1) To or (2) From header with an address that contains a large number of "\" (backslash) characters.

Buffer overflows in PHP before 4.3.3 have unknown impact and unknown attack vectors.

Integer overflows in (1) base64_encode and (2) the GD library for PHP before 4.3.3 have unknown impact and unknown attack vectors.

Integer signedness error in emalloc() function for PHP before 4.3.2 allow remote attackers to cause a denial of service (memory consumption) and possibly execute arbitrary code via negative arguments to functions such as (1) socket_recv, (2) socket_recvfrom, and possibly other functions.

Heap-based buffer overflow in the wordwrap function in PHP after 4.1.2 and before 4.3.0 may allow attackers to cause a denial of service or execute arbitrary code.

php.exe in PHP 3.0 through 4.2.2, when running on Apache, does not terminate properly, which allows remote attackers to cause a denial of service via a direct request without arguments.

The imap_header function in the IMAP functionality for PHP before 4.3.0 allows remote attackers to cause a denial of service via an e-mail message with a large number of "To" addresses, which triggers an error in the rfc822_write_address function.

CRLF injection vulnerability in PHP 4.2.1 through 4.2.3, when allow_url_fopen is enabled, allows remote attackers to modify HTTP headers for outgoing requests by causing CRLF sequences to be injected into arguments that are passed to the (1) fopen or (2) file functions.

The mail function in PHP 4.x to 4.2.2 does not filter ASCII control characters from its arguments, which could allow remote attackers to modify mail message content, including mail headers, and possibly use PHP as a "spam proxy."