#VU33987 CRLF injection in Dropbear - CVE-2016-3116

Vulnerability identifier: #VU33987

Vulnerability risk: Medium

CVSSv4.0: 7.4 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P/U:Green]

CVE-ID: CVE-2016-3116

CWE-ID: CWE-93

Exploitation vector: Network

Exploit availability: Yes

Vulnerable software:
Dropbear
Server applications / Remote management servers, RDP, SSH

Vendor: Matt Johnston

Description

The vulnerability allows a remote user to bypass implemented security restrictions.

The vulnerability exists due to improper input validation when processing CRLF characters. A remote authenticated user bypass intended shell-command restrictions via crafted X11 forwarding data.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Dropbear: 2013.56 - 2015.71

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External links
https://lists.fedoraproject.org/pipermail/package-announce/2016-March/179261.html
https://lists.fedoraproject.org/pipermail/package-announce/2016-March/179269.html
https://lists.fedoraproject.org/pipermail/package-announce/2016-March/179870.html
https://lists.opensuse.org/opensuse-updates/2016-03/msg00105.html
https://lists.opensuse.org/opensuse-updates/2016-03/msg00113.html
https://packetstormsecurity.com/files/136251/Dropbear-SSHD-xauth-Command-Injection-Bypass.html
https://seclists.org/fulldisclosure/2016/Mar/47
https://github.com/tintinweb/pub/tree/master/pocs/cve-2016-3115
https://matt.ucc.asn.au/dropbear/CHANGES
https://security.gentoo.org/glsa/201607-08

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user 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.