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9/24/2014
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Bash Bug May Be Worse Than Heartbleed

Linux, Unix, and Internet of Things devices affected by critical vulnerability.

Though only disclosed this morning, proof-of-concept exploits are already available for a critical remote code execution vulnerability security experts say is more widespread than Heartbleed.

CVE-2014-6271, a vulnerability in the command shell Bash, affects many Linux- and UNIX-based systems. Although no exploits have yet been seen in the wild, the pervasiveness and ease of exploit have earned it a CVSS score of 10.

The bug makes remote code execution possible, even though Bash itself does not handle data from remote users. As Jim Reavis of Cloud Security Alliance wrote today:

Bash is a local shell, it doesn’t handle data supplied from remote users, sono big deal right? Wrong.

A large number of programs on Linux and other UNIX systems use Bash to setup environmental variables which are then used while executing other programs...

In short this vulnerability allows attackers to cause arbitrary command execution, remotely, for example by setting headers in a web request, or by setting weird mime types for example.

Like Heartbleed, the bug may affect a broad swath of systems -- including Apache servers, web servers running CGI scripts, and embedded systems in everything from control systems to medical devices to digital cameras.

Also like Heartbleed, patching every system that uses Bash is going to be difficult. As Robert Graham of Errata Security wrote:

...while the known systems (like your web-server) are patched, unknown systems remain unpatched. We see that with the Heartbleed bug: six months later, hundreds of thousands of systems remain vulnerable. These systems are rarely things like webservers, but are more often things like Internet-enabled cameras.

Internet-of-things devices like video cameras are especially vulnerable because a lot of their software is built from web-enabled bash scripts. Thus, not only are they less likely to be patched, they are more likely to expose the vulnerability to the outside world.

Rapid7 representatives say that they are working on a Metasploit module to exploit the bug; they expect a first version to be available later today.

Meanwhile, Huzaifa Sidhpurwala of Red Hat released a very simple proof-of-concept exploit of this vulnerability that only requires one line of code.

Dave Kennedy, CEO of TrustSec, says that the proof-of-concept is very simple and would blend in with normal activity more smoothly than most malware.

"You should see it in your logs, if you're looking for it," says Kennedy, "but that's about it."

The good news is that patches are already available. Reavis doubts that the patch would cause any performance problems for the applications that use Bash, but some administrators might decide to put up a web application firewall first, then patch when they can.

Kennedy does not believe that the bug is as bad as Heartbleed "yet," but nevertheless he advises you put aside your usual patch testing processes and simply "patch right now."

Sara Peters is Senior Editor at Dark Reading and formerly the editor-in-chief of Enterprise Efficiency. Prior that she was senior editor for the Computer Security Institute, writing and speaking about virtualization, identity management, cybersecurity law, and a myriad ... View Full Bio

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paulvixie
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paulvixie,
User Rank: Author
9/26/2014 | 3:26:11 PM
on mac/os-x and redhat and older debian, bash is used as /bin/sh, and this matters
someone here said that this only hurt cgi-bin's written in bash, and that's not always true. if you are on a redhat or apple or older debian system where bash is used as /bin/sh, then libc will be using bash to execute commands, and this includes apache's CGI data path. libc popen(), system(), execlp(), and execvp() are defined to use the /bin/sh interface. so you could be using bash for a lot of things you didn't know about -- certainly that's how the shellshock day 1 botnet was created, not by finding CGI scripts written in bash, but by finding Apache servers where /bin/sh is bash. of which there are millions.
securityaffairs
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securityaffairs,
User Rank: Ninja
9/26/2014 | 9:28:33 AM
It's critical for IoT devices
The impact of the Bash Bug flaw is critical and worse than Heartbleed because it is quite easy exploitable.

Another element to consider is that while servers are easy to patch, there is a serious impact for those it (Internet of Things) devices are poorly configured and that is not possible to update in a short time for various reasons.

 
TalKlein
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TalKlein,
User Rank: Author
9/25/2014 | 6:25:19 PM
Re: Worse than heartbleed?
Totally agree WRT "Defcon 1".. Especially since there's very little most consumers can do other than wait for vendors to make patches available. It's like not I can tell my mom to go patch bash on her home router :)

I don't know how we solve for that problem. I wish the press would do a better job of communicating risk to the public. But we've become a culture of rubberneckers.
AnonymousMan
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AnonymousMan,
User Rank: Moderator
9/25/2014 | 5:55:05 PM
Re: Worse than heartbleed?
I'm not even arguing that it's not a BFD.  I just think the press needs to come down from defcon 1.  Yes, there are very specific situations where this could matter a lot.  CGI programs that invoke the shell are clearly the biggest concern. GIT and other source code management platforms (any shared Linux environment really) may very well be another, because of the SSH forcecommand issue.  However, attacker still needs a login and still needs to escalate privs.  One would hope that steps are taken in a shared Linux environment to secure against this specific risk.

 

 
TalKlein
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TalKlein,
User Rank: Author
9/25/2014 | 5:26:20 PM
Re: Worse than heartbleed?
Again, if I can do a remote code execution by using something as simple as git, I don't see why you don't see that as a BFD. IMO Heartbleed was a listening/impersonation problem, whereas the ramifications of this are much greater in the context of its ease of exploitation. I have zero skin in this game FUD-wise. If you don't take my word for it, take CERT's
AnonymousMan
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AnonymousMan,
User Rank: Moderator
9/25/2014 | 5:22:33 PM
Re: Worse than heartbleed?
So you pointed out an exploit that looks for vulnerable CGI programs and then fetches a kernel exploit.  It's still looking for vulnerable CGI programs. I'm not trying to suggest this isn't an important vulnerability, but let's stop with the FUD. The number of network calls that result in invocation of a bash shell is relatively limited. Comparing this to Heartbleed at this point and using language like the press has been is just not constructive. CNN..."At its most basic, it lets someone hack every device in your house, business or government building".  Geez.  I think the most significant vector could be DHCP, but I haven't heard anyone suggest that the typical devices that might get DHCP from an untrusted server are impacted (e.g. Android, iOS, etc).
TalKlein
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TalKlein,
User Rank: Author
9/25/2014 | 4:38:52 PM
Re: Worse than heartbleed?
Here's the simple fact, folks: Remote code execution is pretty much the most dangerous class of vulnerability you're going to find. It's not just about CGI, I've been able to do some gnarly stuff with git in my lab, and others have done much much worse
aws0513
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aws0513,
User Rank: Ninja
9/25/2014 | 3:37:02 PM
Re: Worse than heartbleed?
Although I agree the risk factor compared to Heartbleed may not be the same, the broad distribution of systems that have GNU BASH as part of the platform is likely quite broad.
Even if the systems are not currently calling BASH via cgi-bin or any other known vulnerable configuration, every effort should be made to ensure that the vulnerability cannot become a problem in the future.
It is also likely that the dust isn't completely settled in this regard.  Vendors may still be assessing impact on their product platforms and/or developing patches.  I expect several patches for some of our appliance devices that utilize *nix platforms.
AnonymousMan
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AnonymousMan,
User Rank: Moderator
9/25/2014 | 2:38:54 PM
Worse than heartbleed?
That's a huge stretch. Can someone name a few significant products that are anonymously and remotely exploitable without a patch? You know, like Juniper VPN, etc? Apache is NOT vulnerable, some CGI scripts MIGHT be, but only if they call the shell.
aws0513
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aws0513,
User Rank: Ninja
9/25/2014 | 2:28:39 PM
It's been a day
So...  Mentioned this vulnerability to a non-technical manager when I passed him in the hall.
He said "Bash? Is that some kind of video game?"
My response "I wish it were that simple."

:-)
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