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Shellshock DHCP Remote Code Execution – Proof of Concept

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Re: Shellshock DHCP Remote Code Execution – Proof of Concept

#61

Earlier quoted context omitted.

Well, yes. If you were going to exploit CGI scripts you'd likely use wget or curl instead of coding an HTTP client from scratch so why is this suprising?

It's a little surprising because I'm tempted to classify this one as 'requires 0 lines of code'.

its pretty much the same for CGIs, its a one liner. theres other exploits like that. it happens :)

Re: Shellshock DHCP Remote Code Execution – Proof of Concept

#62

Yeah, I don't think anyone has grasped the extent of how dangerous this vuln is -- was it released a little prematurely? is it still in "embargo"? This is hundreds of times worse than heartbleed in terms of scope/attack surface for modern servers... (I say hundreds of times worse because heartbleed was scrape-some-data-till-you-get-private-keys-and-watch-communication, where this is just get-yourself-a-shell-and-pwn-…

On the other hand Windows sysadmins are probably enjoying some schadenfreude right about now.

Re: Shellshock DHCP Remote Code Execution – Proof of Concept

#63
post #25

Earlier quoted context omitted.

NetworkManager's had vulnerabilities over the years ( http://www.cvedetails.com/product/5634/Gnome-Networkmanager.... ), as has systemd. Stating this as a reason to switch is ridiculous. One can easily switch to a much more audited, secure scripting environment, such as ksh, and still have all the power scripting brings.

Not saying I agree with GP, but "the power scripting brings" can be part of the problem. Scripting is used as a means to execute arbitrary commands on a single level privilege (that of the user hooking the scripts, very often root or some high-privilege user) as opposed to a limited set of application-specific functionality. This adds a whole level of complexity to the system, which in security terms is typically the…

pretty much. scripting envs are extremely flexible and powerful, thus very prone to such issues. thats why you dont give user input to shells unless you want the user to have the full shell access. environment included.

Re: Shellshock DHCP Remote Code Execution – Proof of Concept

#64

Does this mean I shouldn't run dhcp servers? Or is even my laptop running a dhcp client going to have a bad time?

This means that DHCP clients that use bash and have DHCP server-controlled environment variables can have commands injected (as root) by a malicious DHCP server. Notably, attackers in an unhardened network can reply to DHCP clients themselves, even if there's already a DHCP server on the network. So it's not just the sysadmin who can exploit this, but anyone on the same network (broadcast domain) as the vulnerable DH…

why is a DHCP client calling bash for anything ? that's just a terrible way to program. and doubly so for passing unscrubbed data to it as environment variables

Re: Shellshock DHCP Remote Code Execution – Proof of Concept

#65

Yeah, I don't think anyone has grasped the extent of how dangerous this vuln is -- was it released a little prematurely? is it still in "embargo"? This is hundreds of times worse than heartbleed in terms of scope/attack surface for modern servers... (I say hundreds of times worse because heartbleed was scrape-some-data-till-you-get-private-keys-and-watch-communication, where this is just get-yourself-a-shell-and-pwn-…

"At present, public disclosure is scheduled for Wednesday, 2014-09-24 14:00 UTC. We do not expect the schedule to change, but we may be forced to revise it." http://seclists.org/oss-sec/2014/q3/650

Re: Shellshock DHCP Remote Code Execution – Proof of Concept

#66

Earlier quoted context omitted.

Assuming it's a network full of machines who haven't bothered updating yet. EDIT: right?

Um, "haven't bothered"? Think about all the Linux/Unix -based devices that could be affected here, it's in the millions. Do you run a local server on your box? How about your Linux-based router? Has it been patched yet? Why not, it's been more than 24 hours now.

How many of them run bash? I'm about to check my router (I didn't think of it until today), but I read that Tomato runs busybox which I understand is not affected.

Re: Shellshock DHCP Remote Code Execution – Proof of Concept

#67
post #62

Yeah, I don't think anyone has grasped the extent of how dangerous this vuln is -- was it released a little prematurely? is it still in "embargo"? This is hundreds of times worse than heartbleed in terms of scope/attack surface for modern servers... (I say hundreds of times worse because heartbleed was scrape-some-data-till-you-get-private-keys-and-watch-communication, where this is just get-yourself-a-shell-and-pwn-…

On the other hand Windows sysadmins are probably enjoying some schadenfreude right about now.

While not exactly thrilled, as a Linux user I have to admit it's only fair. That's exactly what some of us did all those years when Windows used to have more holes than Linux. Ah well, back to BSD I guess...

Re: Shellshock DHCP Remote Code Execution – Proof of Concept

#69
post #62

Yeah, I don't think anyone has grasped the extent of how dangerous this vuln is -- was it released a little prematurely? is it still in "embargo"? This is hundreds of times worse than heartbleed in terms of scope/attack surface for modern servers... (I say hundreds of times worse because heartbleed was scrape-some-data-till-you-get-private-keys-and-watch-communication, where this is just get-yourself-a-shell-and-pwn-…

On the other hand Windows sysadmins are probably enjoying some schadenfreude right about now.

It's mostly Linux issue because bash is there installed by default and even /bin/sh is really bash...

For example on BSD you could technically install bash, but chances that it is used as a shell for a services is very small.

Re: Shellshock DHCP Remote Code Execution – Proof of Concept

#70

Earlier quoted context omitted.

Assuming it's a network full of machines who haven't bothered updating yet. EDIT: right?

Um, "haven't bothered"? Think about all the Linux/Unix -based devices that could be affected here, it's in the millions. Do you run a local server on your box? How about your Linux-based router? Has it been patched yet? Why not, it's been more than 24 hours now.

> Linux/Unix-based

Actually it's primarily Linux because /bin/sh is pointing to bash.

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