Denial of service in OpenSSH for Ubuntu

1) Denial of service

EUVDB-ID: #VU1033

Risk: Medium

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:Green]

CVE-ID: CVE-2016-8858

CWE-ID: CWE-401 - Missing release of memory after effective lifetime

Exploit availability: No

Description

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

The weakness is due to flaw in kex_input_kexinit() function. By sending a specially crafted data during the key exchange process, attackers can cause memory exhaustion. Consuming up to 128 MB per connection may lead to denial of service.

Successful exploitation of the vulnerability results in denial of service of the vulnerable system.

Mitigation

Install the latest OpenSSH version 7.4.

Vulnerable software versions

openssh (Ubuntu package): 1:5.9p1-5ubuntu1.4 - 6.6p1-hpn14v5-1~ubuntu14.04.1

CPE2.3

• cpe:2.3:a:canonical:openssh_ubuntu_package:1:5.9p1-5ubuntu1.4:*:*:*:*:ubuntu:*:*
• cpe:2.3:a:canonical:openssh_ubuntu_package:1:5.9p1-5ubuntu1.10:*:*:*:*:ubuntu:*:*
• cpe:2.3:a:canonical:openssh_ubuntu_package:1:6.6p1-2ubuntu2.7:*:*:*:*:ubuntu:*:*

External links

https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/kex.c?rev=1.127&content-type=text/x-cvsweb-markup
https://www.openssh.com/txt/release-7.4

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.