#VU6662 CRLF injection in OpenVPN Access Server - CVE-2017-5868


| Updated: 2017-05-24

Vulnerability identifier: #VU6662

Vulnerability risk: Medium

CVSSv4.0: 1.2 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2017-5868

CWE-ID: CWE-113

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
OpenVPN Access Server
Server applications / Remote access servers, VPN

Vendor: OpenVPN

Description

The vulnerability allows a remote attacker to inject arbitrary session cookies and gain control over victim's VPN session.

The vulnerability exists due to insufficient sanitization of user-supplied data (e.g. %0A character), passed via URL. A remote attacker can create a specially crafted link, trick the victim into following it and spoof HTTP headers, used by OpenVPN Access Server to authenticate users.

Successful exploitation of the vulnerability may allow an attacker to inject arbitrary cookie values, including session identifier, and gain full access to victim's session.

Exploitation example for injecting victim's session identifier, controlled by the attacker:

https://[host]/__session_start__/%0aSet-Cookie:
openvpn_sess_******=******cf23; Path=/; Secure; HttpOnly

Mitigation
Cybersecurity Help is currently unaware of any official solution to address this vulnerability.

Vulnerable software versions

OpenVPN Access Server: 2.1.0 - 2.1.4


External links
https://seclists.org/oss-sec/2017/q2/332


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.


Latest bulletins with this vulnerability