The last few days has seen several vulnerabilities disclosed that include serious gaps in logic with regard to exploitation vectors. What is being called “remote” is not. What is being called “critical” is not. Here are a few examples to highlight the problem. We beg of you, please be rational when explaining vulnerabilities and exploit chaining. The biggest culprit in all of this is the “need for a user to install a malicious app” to then allow a vulnerability to be exploited. Think about it.
We start with an H-Online article titled “Critical vulnerability in Blackberry 10 OS“. First word, critical. In the world of vulnerabilities, critical means a CVSSv2 score of 10.0 which essentially allows for remote code execution without user interaction. Consider that standard and widely accepted designation, and read the article’s summary of what is required to exploit this vulnerability:
As well as needing Protect enabled, the user must still install a malicious app, which then compromises a Protect-component so that it can intercept a password reset. This password reset requires the user, or someone who knows the BlackBerry ID and password, to go to the web site of BlackBerry Protect and request the password. If the attacker manages that, then the Protect component, compromised by the earlier malicious app, can let the attacker know the new password for the device. If he has physical access to the device, he can now log on successfully as the actual user. Otherwise, the attacker can only access Wi-Fi file sharing if the actual user has activated it.
The only thing missing from this exploit chain are the proverbial chicken sacrifices at midnight on a full blue moon. Want to get the same result much easier? Find your victim and say “Wow, that is a slick new phone, can I see it?” Nine out of ten times, they unlock the phone and hand it to you. Less work, same result.
#1 – The Galapagos Browser application for Android does not properly implement the WebView class, which allows attackers to obtain sensitive information via a crafted application.
Despite all these references, users are left with either incorrect or very misleading information. First, CVE says “an attacker” instead of qualifying it as a local attacker. I only call them out because they are historically more precise than this. Second, NVD calls this a “context-dependent” attacker via the CVSSv2 score (AV:N/AC:M/Au:N/C:P/I:N/A:N), saying it can be exploited over the network with moderate user interaction. NVD also says this affects confidentiality ‘partially’. JVN goes so far to say it can be exploited “over the Internet using packets” with “anonymous or no authentication”.
The reality of these vulnerabilities is that they are not remote. Not in any form under any circumstances that the vulnerability world accepts. For some reason, VDBs are starting to blur the lines of exploit traits when it comes to mobile devices. The thought process seems to be that if the user installs a malicious application, then the subsequent local vulnerability becomes ‘remote’. This is absurd. Just because that may be the most probable exploit vector and chaining, does not change the fact that getting a user to install a malicious application is a separate distinct vulnerability that cannot have any scoring weight or impact applied to the vulnerability in question. If you can get a phone user to install a malicious application, you can do a lot more than steal ‘partial’ information from the one vulnerable application.
Let me put it to you in terms that are easier to understand. If you have a Windows local privilege escalation vulnerability, it is local. Using the above logic, if I say that by tricking a user into installing a malicious application it can then be exploited remotely, what would you say? If you have a Linux Kernel local DoS, it too can become remote or context-dependent, if the root user installs a malicious application. You can already spin almost any of these local vulnerabilities into remote by saying “remote, authentication required” and assuming it can be done via RDP or SSH. To do so though, devaluates the entire purpose of vulnerability classification.
Any doubts? Consider that CVE treats the exact same situation as the mobile browser vulnerabilities above as a local issue in Windows, even when a “crafted application” is required (see IDs below). The only difference is if the local user writes the application (Windows), or gets the user to install the application (Mobile). Either way, that is a local issue.
The Open Security Foundation (OSF) and Risk Based Security wrote an open letter to FIRST regarding the upcoming Common Vulnerability Scoring System (CVSS) version 3 proposal. While we were not formally asked to provide input, given the expertise of managing vulnerability databases, along with the daily use of CVSS, we felt the feedback would provide valuable insight to improve CVSS in the future.
Some of the areas discussed include:
- Introducing 4 levels for granularity
- Better definitions for terminology for more accurate scoring
- Re-examining the pitfalls of “Access Complexity”
- Limitations of the current Access Vector breakdown
- The challenge of scoring authentication
- And a variety of other considerations to improve vulnerability scoring
Our conclusion points to the need for CVSS to be overhauled as CVSSv2 has too many current shortcomings to provide an adequate and useful risk scoring model. You can download the full letter in PDF format.