Ubuntu update for openssh

Published: 2021-08-12 | Updated: 2023-03-09

Risk	Medium
Patch available	YES
Number of vulnerabilities	2
CVE-ID	CVE-2016-10708 CVE-2018-15473
CWE-ID	CWE-476 CWE-388
Exploitation vector	Network
Public exploit	Public exploit code for vulnerability #2 is available.
Vulnerable software	Ubuntu Operating systems & Components / Operating system openssh-server (Ubuntu package) Operating systems & Components / Operating system package or component
Vendor	Canonical Ltd.

Security Bulletin

This security bulletin contains information about 2 vulnerabilities.

1) Null pointer dereference

EUVDB-ID: #VU14163

Risk: Low

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2016-10708

CWE-ID: CWE-476 - NULL Pointer Dereference

Exploit availability: No

Description

The vulnerability allows a remote attacker to cause DoS condition on the target system.

The vulnerability exists due to improper processing of out-of-sequence NEWKEYS messages, as defined in the kex.c and packet.c source code files. A remote attacker can send an out-of-sequence NEWKEYS message, trigger a NULL pointer dereference condition and cause the sshd daemon to crash.

Mitigation

Update the affected package openssh to the latest version.

Vulnerable software versions

Ubuntu: 18.04

openssh-server (Ubuntu package): before 1:7.6p1-4ubuntu0.5

CPE2.3

External links

https://ubuntu.com/security/notices/USN-3809-2

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) User enumeration

EUVDB-ID: #VU14440

Risk: Medium

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

CVE-ID: CVE-2018-15473

CWE-ID: CWE-388 - Error Handling

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to enumerate all accounts on the system.

The vulnerability exists due to a logical error in auth2-gss.c, auth2-hostbased.c, and auth2-pubkey.c files when processing authentication requests. A remote attacker can send a specially crafted chain of packets and monitor behavior of openssh server to determine presence of a valid username. The server will drop connection upon receiving a malformed authentication packets if the username is valid.

Mitigation

Update the affected package openssh to the latest version.

Vulnerable software versions

Ubuntu: 18.04

openssh-server (Ubuntu package): before 1:7.6p1-4ubuntu0.5

CPE2.3

External links

https://ubuntu.com/security/notices/USN-3809-2

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, a fully functional exploit for this vulnerability is available.