Udp.c in Linux kernel pre-4.5 allows remote attackers to execute arbitrary code

I never used the MSG_PEEK flag, but over 15 years ago (maybe it wasnt implemented yet?) I accomplished a similar task by using the SO_REUSEADDR and SO_REUSEPORT flags which worked nicely on Windows too. The goal was to have several UDP "agents" listening on the same port on the same machine (which would normally raise an EADDRINUSE error), all of them examining a packet and acting upon a header contained in that packet. All them would receive a copy of the packet on their respective socket (that was the flags purpose), so that they could filter it and act only if the header contained data relative to that agent. This allowed a very modular approach where once the protocol was defined I could compile only the agent I needed without touching the others.

As far as I can tell, a packet from a non-localhost source may be received, but (obviously) the udp_recvmsg does not get called since the system call is not triggered.

Unfortunately, there is a large amount of devices such as home routers, televisions, phones, etc, that are completely impossible to update. So, being aware of cases of software that actually use MSG_PEEK might be useful.

[1] Really, there isn't any distinction at the kernel level between a UDP "client" and "server". It's the same set of syscalls being used on both sides, the difference is just who speaks first.

Edit: Ubuntu's tracker is at https://people.canonical.com/~ubuntu-security/cve/2016/CVE-2...

Most servers/business run on (not the latest) redhat/suse/debian/ubuntu and derivates. They dont have kernel versions that recent.

http://lxr.free-electrons.com/source/net/core/datagram.c?v=3...

http://lxr.free-electrons.com/source/net/core/datagram.c?v=4...

http://lxr.free-electrons.com/source/net/core/datagram.c?v=4...

I am just trying to completely understand the bug, I wonder if it really was unexploitable before the patch. Got any source for that?

EDIT: sorry, misunderstood your message / mixed up commits, I was looking into when 89c22d8c3b27 hit mainline, which causes the vulnerable code path.

Someone can write a little piece of code that scans for random hosts, runs the attack and installs itself on the target system which then does the same until it's taken over all vulnerable hosts. It can self-replicate extremely fast.

This was a huge issue back in the Blaster/Sasser days of early Windows XP when plugging in a machine to the internet directly was common.

Servers and home routers are often plugged into the internet directly and often run Linux. So if this is easily exploitable it could turn into a real disaster.

Heartbleed can't be turned into a worm because there's no code execution, just information disclosure, with this there is.

Unlike many other viruses, you don't have to visit a page that runs an exploit, download a trojan, open an attachment, or do anything else to trigger it. Any computer that can contact the exploitable service can infect you (and will, if it has the worm too).

"Worm-level" would call back to classic worm attacks where any computer connected to the internet and running Windows 2000/XP was at real risk of infection just by being connected. LAN/corporate networks could be infected if someone plugged an infected computer into the LAN, or if it spread through the DMZ.

This type of attack doesn't happen very often anymore, as almost all home connections are firewalled by default, vendors have become more careful with security, etc.