The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers). An example of a network attack is an attacker causing a denial of service by sending a specially crafted TCP packet across a wide area network (e.g., CVE-2004-0230).
Attack Complexity
High
AC
The successful attack depends on the evasion or circumvention of security-enhancing techniques in place that would otherwise hinder the attack. These include: Evasion of exploit mitigation techniques. The attacker must have additional methods available to bypass security measures in place. For example, circumvention of address space randomization (ASLR) or data execution prevention must be performed for the attack to be successful. Obtaining target-specific secrets. The attacker must gather some target-specific secret before the attack can be successful. A secret is any piece of information that cannot be obtained through any amount of reconnaissance. To obtain the secret the attacker must perform additional attacks or break otherwise secure measures (e.g. knowledge of a secret key may be needed to break a crypto channel). This operation must be performed for each attacked target.
Privileges Required
None
PR
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction
None
UI
The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges
Scope
Unchanged
S
An exploited vulnerability can only affect resources managed by the same security authority. In the case of a vulnerability in a virtualized environment, an exploited vulnerability in one guest instance would not affect neighboring guest instances.
Confidentiality
High
C
There is total information disclosure, resulting in all data on the system being revealed to the attacker, or there is a possibility of the attacker gaining control over confidential data.
Integrity
High
I
There is a total compromise of system integrity. There is a complete loss of system protection, resulting in the attacker being able to modify any file on the target system.
Availability
High
A
There is a total shutdown of the affected resource. The attacker can deny access to the system or data, potentially causing significant loss to the organization.
PHP 7.0.10 Heap overflow in mysqlnd related to BIT fieldsDescription:
------------
mysqlnd extension assumes the `flags` returned for a BIT field necessarily contain UNSIGNED_FLAG; this might not be the case, with a rogue mysql server, or a MITM attack.
In php_mysqlnd_rowp_read_text_protocol_aux (mysqlnd_wireprotocol.c) BIT fields are treated specially and use extra space pre-allocated for that processing at the end of `row_buffer` (see the comment there).
The size of that extra space that is allocated is calculated in mysqlnd_res_meta::read_metadata (in mysqlnd_result_meta.c), and depends on the number of BIT fields and their respective size in bytes. For a BIT(8) field, which has 8 bits, the function reserves 3 bytes. This is fine if the field is UNSIGNED (which BIT values should always be with a normal mysql server), however if the server returns BIT fields without the UNSIGNED_FLAG set, a BIT(8) will then be interpreted as signed, and can contain negative values such as -127, which no longer fit the reserved space:
To read BIT values off a row_buffer, php_mysqlnd_rowp_read_text_protocol_aux uses the generic function ps_fetch_from_1_to_8_bytes (mysqlnd_ps_codec.c) which starts exactly with a check of the UNSIGNED_FLAG but is not aware of whether it is processing a BIT field.
Thus, a malicious mysql server or MITM can return field metadata for BIT fields that does not contain the UNSIGNED_FLAG, leading to a heap overflow.
Tested in 5.6.x and latest packaged PHP 7.0.7, but should affect a lot more versions. Affects queries through mysql / mysqli / anything that uses mysqlnd.
To simulate a rogue mysql server apply the following patch to mysqlnd_ps_codec.c before running the test case:
< if (field->flags & UNSIGNED_FLAG) {
> if (field->flags & UNSIGNED_FLAG && field->type != MYSQL_TYPE_BIT) {
Test script:
---------------
<?php
/*
Please setup the following database/table:
CREATE DATABASE php; USE php;
CREATE TABLE `php` (`moo` bit(8) DEFAULT NULL ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
INSERT INTO `php` VALUES (0x81); # -127 when signed
*/
$link = mysqli_connect('127.0.0.1', 'root', '', 'php');
if (!$link) die("Cannot connect");
$s = str_repeat("moo,", 60000); /* can play with this value a bit to see different corruption */
$result = mysqli_query($link, "SELECT $s 1 FROM php");
while($row = mysqli_fetch_row($result)) { $v = print_r($row, true); /* just to exercise heap */};
mysqli_close($link);
?>
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