Ubuntu update for OpenSSH
| Risk | Medium |
| Patch available | YES |
| Number of vulnerabilities | 2 |
| CVE-ID | CVE-2016-6210 CVE-2016-6515 |
| CWE-ID | CWE-200 CWE-400 |
| Exploitation vector | Network |
| Public exploit |
Public exploit code for vulnerability #1 is available. Public exploit code for vulnerability #2 is available. |
| Vulnerable software Subscribe |
openssh (Ubuntu package) Operating systems & Components / Operating system package or component |
| Vendor | Canonical Ltd. |
Security Bulletin
This security bulletin contains information about 2 vulnerabilities.
1) User enumeration via covert timing channel
EUVDB-ID: #VU255
Risk: Medium
CVSSv3.1: 4.9 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N/E:F/RL:O/RC:C]
CVE-ID: CVE-2016-6210
CWE-ID:
CWE-200 - Information exposure
Exploit availability: Yes
DescriptionThe vulnerability allows a remote attacker to enumerate users on system.
The vulnerability exists in most systems where the Blowfish algorithm runs faster than SHA256/SHA512. A remote unauthenticated attacker can determine valid usernames by sending a specially crafted request with a large password (approximately 10,000 characters) to the target ssh daemon. On systems where a valid user's password has been hashed with SHA256/SHA512, the response time will be shorter for a non-existent username than for a valid username.
Successful exploitation of this vulnerability may result in disclosure or user logins.
MitigationUpdate the affected packages.
- Ubuntu 16.04 LTS:
- openssh-server 1:7.2p2-4ubuntu2.1
- Ubuntu 14.04 LTS:
- openssh-server 1:6.6p1-2ubuntu2.8
- Ubuntu 12.04 LTS:
- openssh-server 1:5.9p1-5ubuntu1.10
openssh (Ubuntu package): 1:5.9p1-5ubuntu1.1 - 1:6.6p1-2ubuntu2.6
External linkshttp://www.ubuntu.com/usn/usn-3061-1/
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, a fully functional exploit for this vulnerability is available.
2) Consuming excessive CPU resources on the target system
EUVDB-ID: #VU252
Risk: Medium
CVSSv3.1: 7.7 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:P/RL:O/RC:C]
CVE-ID: CVE-2016-6515
CWE-ID:
CWE-400 - Resource exhaustion
Exploit availability: Yes
DescriptionThe vulnerability allows a remote attacker to consume excessive CPU resources on the target system.
The vulnerability exists in the crypt(3) function, which accepts passwords longer that 1024 characters in auth_password() function in the auth_passwd.c . A remote unauthenticated attacker can submit a very long string as a password and consume excessive CPU resources.
Successful exploitation of this vulnerability may result in denial of service.
MitigationUpdate the affected packages.
- Ubuntu 16.04 LTS:
- openssh-server 1:7.2p2-4ubuntu2.1
- Ubuntu 14.04 LTS:
- openssh-server 1:6.6p1-2ubuntu2.8
- Ubuntu 12.04 LTS:
- openssh-server 1:5.9p1-5ubuntu1.10
openssh (Ubuntu package): 1:5.9p1-5ubuntu1.1 - 1:6.6p1-2ubuntu2.6
External linkshttp://www.ubuntu.com/usn/usn-3061-1/
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.
