! Please share this post with people who are hosting a CS:GO server and want to fix this issue !

If you have a CS:GO (NOT CS2) server, users can't join your server IF they are using the archived version of CS:GO (app/4465480/CounterStrike_Global_Offensive/). If you want to allow those users to join, follow this guide.

!THIS ONLY WORKS IF YOU ARE THE SERVER OWNER WITH ACCESS TO THE SERVER FILES!

STORY & TUTORIAL

Valve archived CS:GO and made it available as a separate Steam app. The problem is that clients using the archived build can't connect to community servers.

The auth ticket comes in with a mismatched appid and the server rejects it:

S3: Client connected with ticket for the wrong game
RejectConnection: STEAM validation rejected

Root cause

The engine has a jump table dispatch that handles appid validation. Case 4 (archived build) hits a rejection path instead of the default OK path.

Fix: SourceMod Extension (recommended)

Download the extension and drop these files into your server:

addons/sourcemod/extensions/csgo_steamfix.ext.so       <- Linux
addons/sourcemod/extensions/csgo_steamfix.ext.dll      <- Windows

addons/sourcemod/extensions/csgo_steamfix.autoload     <- auto-load trigger (empty file)

The extension loads automatically on server start, patches the engine, and restores the original state on unload. (Works on both Linux and Windows)

If it works, you'll see this in the console / steamfix.log (Windows):

[steamfix] loading..
[steamfix] engine patched!

After this, everyone can connect, archived build clients included.

You can download the extension from the repo: https://github.com/eonexdev/csgo-sv-fix-engine

Manual fix (only if you know reverse engineering):

Find the jmp dispatch via IDA (sigmaker):

Linux: FF 24 85 ? ? ? ? 8D B4 26 ? ? ? ? 31 F6
Windows: FF 24 85 ? ? ? ? FF 75 ? 68

That's jmp ds:jpt[eax*4]. Then locate the jump table:

Linux (.rodata:jpt_18A2BA):

• [0] → default (status OK)
• [4] → loc_18A3D8 ← rejection path

Solution: copy jt[0] into jt[4] at runtime.

Windows (.text:jpt_1BF138):

• The compiler emits dec eax before the dispatch, so case 4 maps to index 3
• [3] → loc_1BF189 ← rejection path
• The success path (def_1BF138) is NOT in the table, it's reached via a ja instruction
• Compute its address from the ja rel32 sitting 6 bytes before the jmp ds:jpt
• Write that address into jt[3]

The table address is embedded in the instruction itself (FF 24 85 [addr]), so no separate signature is needed for the table.

Should work on any engine version, just find the jmp dispatch and identify which table index maps to the wrong-game rejection case.

Note on the old method

The original fix was a Linux-only shared lib loaded via LD_PRELOAD:

LD_PRELOAD=/home/container/csgo_steamfix.so ./srcds_run -game csgo

That still works if you prefer it, but the SourceMod extension is easier to use, works on Windows too, and (properly) restores the engine state on unload.