||RealVNC 4.1.1, and other products that use RealVNC such as AdderLink IP and Cisco CallManager, allows remote attackers to bypass authentication via a request in which the client specifies an insecure security type such as "Type 1 - None", which is accepted even if it is not offered by the server, as originally demonstrated using a long password.
|Base: ||7.5 (as of 16-05-2006 - 14:57)|
An attacker obtains unauthorized access to an application, service or device either through knowledge of the inherent weaknesses of an authentication mechanism, or by exploiting a flaw in the authentication scheme's implementation. In such an attack an authentication mechanism is functioning but a carefully controlled sequence of events causes the mechanism to grant access to the attacker. This attack may exploit assumptions made by the target's authentication procedures, such as assumptions regarding trust relationships or assumptions regarding the generation of secret values. This attack differs from Authentication Bypass attacks in that Authentication Abuse allows the attacker to be certified as a valid user through illegitimate means, while Authentication Bypass allows the user to access protected material without ever being certified as an authenticated user. This attack does not rely on prior sessions established by successfully authenticating users, as relied upon for the "Exploitation of Session Variables, Resource IDs and other Trusted Credentials" attack patterns.
Exploiting Trust in Client (aka Make the Client Invisible)
An attack of this type exploits a programs' vulnerabilities in client/server communication channel authentication and data integrity. It leverages the implicit trust a server places in the client, or more importantly, that which the server believes is the client.
An attacker executes this type of attack by placing themselves in the communication channel between client and server such that communication directly to the server is possible where the server believes it is communicating only with a valid client.
There are numerous variations of this type of attack.
Utilizing REST's Trust in the System Resource to Register Man in the Middle
This attack utilizes a REST(REpresentational State Transfer)-style applications' trust in the system resources and environment to place man in the middle once SSL is terminated. Rest applications premise is that they leverage existing infrastructure to deliver web services functionality. An example of this is a Rest application that uses HTTP Get methods and receives a HTTP response with an XML document. These Rest style web services are deployed on existing infrastructure such as Apache and IIS web servers with no SOAP stack required. Unfortunately from a security standpoint, there frequently is no interoperable identity security mechanism deployed, so Rest developers often fall back to SSL to deliver security. In large data centers, SSL is typically terminated at the edge of the network - at the firewall, load balancer, or router. Once the SSL is terminated the HTTP request is in the clear (unless developers have hashed or encrypted the values, but this is rare). The attacker can utilize a sniffer such as Wireshark to snapshot the credentials, such as username and password that are passed in the clear once SSL is terminated.
Once the attacker gathers these credentials, they can submit requests to the web service provider just as authorized user do. There is not typically an authentication on the client side, beyond what is passed in the request itself so once this is compromised, then this is generally sufficient to compromise the service's authentication scheme.
Man in the Middle Attack
This type of attack targets the communication between two components (typically client and server). The attacker places himself in the communication channel between the two components. Whenever one component attempts to communicate with the other (data flow, authentication challenges, etc.), the data first goes to the attacker, who has the opportunity to observe or alter it, and it is then passed on to the other component as if it was never intercepted. This interposition is transparent leaving the two compromised components unaware of the potential corruption or leakage of their communications. The potential for Man-in-the-Middle attacks yields an implicit lack of trust in communication or identify between two components.
|description||RealVNC Authentication Bypass. CVE-2006-2369. Remote exploit for windows platform |
|last seen||2016-02-02 |
|title||RealVNC - Authentication Bypass |
|description||RealVNC 4.1.0 - 4.1.1 (VNC Null Authentication) Auth Bypass Patch/EXE. CVE-2006-2369. Remote exploits for multiple platform |
|last seen||2016-01-31 |
|title||RealVNC 4.1.0 - 4.1.1 - VNC Null Authentication Bypass Patched EXE |
|description||This module exploits an Authentication bypass Vulnerability in RealVNC Server version 4.1.0 and 4.1.1. It sets up a proxy listener on LPORT and proxies to the target server The AUTOVNC option requires that vncviewer be installed on the attacking machine. |
|last seen||2019-03-19 |
|title||RealVNC NULL Authentication Mode Bypass |
|NASL family||FreeBSD Local Security Checks |
|NASL id||FREEBSD_PKG_4645B98CE46E11DA9AE700123FCC6E5C.NASL |
|description||RealVNC is susceptible to an authentication-bypass vulnerability. A malicious VNC client can cause a VNC server to allow it to connect without any authentication regardless of the authentication settings configured in the server. Exploiting this issue allows attackers to gain unauthenticated, remote access to the VNC servers. |
|last seen||2019-02-21 |
|plugin id||21574 |
|title||FreeBSD : vnc -- authentication bypass vulnerability (4645b98c-e46e-11da-9ae7-00123fcc6e5c) |
|NASL family||Misc. |
|NASL id||REALVNC_AUTH_BYPASS.NASL |
|description||The version of VNC server running on the remote host is affected by the following vulnerabilities :
- A flaw exists in RealVNC due to an error when handling password authentication. A remote attacker can exploit this to bypass authentication by using a specially crafted request in which the client specifies an insecure security type (e.g., 'Type 1 - None'), which is accepted even if not offered by the server.
- A flaw exists in LibVNCServer within file auth.c due to an error when handling password authentication. A remote attacker can exploit this to bypass authentication by using a specially crafted request in which the client specifies an insecure security type (e.g., 'Type 1 - None'), which is accepted even if not offered by the server. (CVE-2006-2450) |
|last seen||2019-02-21 |
|plugin id||21564 |
|title||VNC Security Type Enforcement Failure Remote Authentication Bypass |
|contributor||Mark J Cox |
|organization||Red Hat |
|statement||This issue only affected version 4.1.1 and not the versions distributed with Red Hat Enterprise Linux 2.1, 3, or 4. |
|Last major update
||17-10-2016 - 23:39
||15-05-2006 - 12:06
||18-10-2018 - 12:39