Ubuntu update for OpenSSH

Published: 2019-02-07 | Updated: 2019-02-11

Risk	Low
Patch available	YES
Number of vulnerabilities	3
CVE-ID	CVE-2018-20685 CVE-2019-6109 CVE-2019-6111
CWE-ID	CWE-284 CWE-451 CWE-20
Exploitation vector	Network
Public exploit	Public exploit code for vulnerability #3 is available.
Vulnerable software	openssh (Ubuntu package) Operating systems & Components / Operating system package or component
Vendor	Canonical Ltd.

Security Bulletin

This security bulletin contains information about 3 vulnerabilities.

1) Security restrictions bypass

EUVDB-ID: #VU16946

Risk: Low

CVSSv4.0: 2.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2018-20685

CWE-ID: CWE-284 - Improper Access Control

Exploit availability: No

Description

The vulnerability allows a remote attacker to bypass security restrictions on the target system.

The vulnerability exists due to improper validation of filenames by the scp.c source code file in the SCP client . A remote unauthenticated attacker can trick the victim into accessing a file with the filename of . or an empty filename from an attacker-controlled Secure Shell (SSH) server to bypass access restrictions on the system, which could be used to conduct further attacks.

Mitigation

Update the affected packages.

Ubuntu 18.10: openssh-client - 1:7.7p1-4ubuntu0.2
Ubuntu 18.04 LTS: openssh-client - 1:7.6p1-4ubuntu0.2
Ubuntu 16.04 LTS: openssh-client - 1:7.2p2-4ubuntu2.7
Ubuntu 14.04 LTS: openssh-client - 1:6.6p1-2ubuntu2.12

Vulnerable software versions

openssh (Ubuntu package): 1:6.6p1-2ubuntu2.2 - 1:7.7p1-4ubuntu0.1

CPE2.3

External links

https://usn.ubuntu.com/3885-1/

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.

2) Spoofing attack

EUVDB-ID: #VU16990

Risk: Low

CVSSv4.0: 1.7 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2019-6109

CWE-ID: CWE-451 - User Interface (UI) Misrepresentation of Critical Information (Clickjacking, spoofing)

Exploit availability: No

Description

The vulnerability allows a remote attacker to conduct spoofing attack on the target system.

The weakness exists due to accepting and displaying arbitrary stderr output from the scp server by the scp client. A malicious SCP server can use the object name to manipulate the client output, for example to employ ANSI codes to hide additional files being transferred.

Mitigation

Update the affected packages.

Ubuntu 18.10: openssh-client - 1:7.7p1-4ubuntu0.2
Ubuntu 18.04 LTS: openssh-client - 1:7.6p1-4ubuntu0.2
Ubuntu 16.04 LTS: openssh-client - 1:7.2p2-4ubuntu2.7
Ubuntu 14.04 LTS: openssh-client - 1:6.6p1-2ubuntu2.12

Vulnerable software versions

openssh (Ubuntu package): 1:6.6p1-2ubuntu2.2 - 1:7.7p1-4ubuntu0.1

CPE2.3

External links

https://usn.ubuntu.com/3885-1/

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.

3) Security restrictions bypass

EUVDB-ID: #VU16988

Risk: Low

CVSSv4.0: 6.9 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P/U:Clear]

CVE-ID: CVE-2019-6111

CWE-ID: CWE-20 - Improper input validation

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to bypass security restrictions on the target system.

The weakness exists due to missing received object name validation by the scp client. A malicious SCP server can overwrite arbitrary files in the SCP client target directory. If a recursive operation (-r) is performed, the server can manipulate subdirectories as well (for example overwrite .ssh/authorized_keys).

Mitigation

Update the affected packages.

Ubuntu 18.10: openssh-client - 1:7.7p1-4ubuntu0.2
Ubuntu 18.04 LTS: openssh-client - 1:7.6p1-4ubuntu0.2
Ubuntu 16.04 LTS: openssh-client - 1:7.2p2-4ubuntu2.7
Ubuntu 14.04 LTS: openssh-client - 1:6.6p1-2ubuntu2.12

Vulnerable software versions

openssh (Ubuntu package): 1:6.6p1-2ubuntu2.2 - 1:7.7p1-4ubuntu0.1

CPE2.3

External links

https://usn.ubuntu.com/3885-1/

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.