HackerOne has just announced that the way server browser on Steam worked had led to players being able to look up servers for some titles. Team Fortress 2, CS:GO, and Half-Life 2 are also on this list.

The people behind this finding said that they had successfully found the attack vector on Window. However, it also appeared on OS X and Linux but so far, they had had no luck doing the same thing on these two operating systems.

Steam Windows Xp Vista
This vulnerability works on Window

According to them, the success rate of this method is 0.2%, which is highly dangerous considering the massive number of players on Steam. They calculated that with every 512 attempts, one more player would fall victim of the attackers.

That is not the worst of it. This server vulnerability can be combined with a memory bug to increase the success rate. If attackers choose to go this way, no account on Steam can get away untouched, said the researchers.

To back their finding, the researchers make a test server and explained that any Steam’s players who access to information on that server will likely open a way for attackers to execute arbitrary code on their computers. That is just the first step but it can make or break the whole malicious scheme. If it has been achieved, attackers can do almost anything with the account, from taking away items, assuming control of the account, to infecting the computer with even more malware.

Steam Bug Game Codes
When they are able to execute arbitrary code. there is nothing else they cannot do

In answer for this announcement, Valve said that they had fixed the bug on Linux, Window, and OS X. The first time this vulnerability was mentioned was in December 2018 and Valve gave the team a total of $18,000 as bounty, $15,000 as the award and $3,000 as a bonus.

However, there is still a pressing question of whether attackers had already exploited the vulnerability before Valve patched it.