GHSA-HVM9-WC8J-MGRC

TShock Security Escalation Exploit

Workarounds

Implement a RemoteClient reset event handler in a plugin like so:

public override void Initialize()
{
        On.Terraria.RemoteClient.Reset += RemoteClient_Reset;
}

private static void RemoteClient_Reset(On.Terraria.RemoteClient.orig_Reset orig, RemoteClient client)
{
	client.ClientUUID = null;
        orig(client);
}

An issue with the way OTAPI manages client connections results in stale UUIDs remaining on RemoteClient instances after a player disconnects.

Because of this, if the following conditions are met a player may assume the login state of a previously connected player:

1. The server has UUID login enabled
2. An authenticated player disconnects
3. A subsequent player connects with a modified client that does not send the ClientUUID#68 packet during connection
4. The server assigns the same RemoteClient object that belonged to the originally authenticated player to the newly connected player

The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.

Kodem intelligence

Already deployed Kodem?

TShock 5.2.1 hotfixes this issue. A more robust fix will be made to OTAPI itself.

1. What is GHSA-HVM9-WC8J-MGRC? GHSA-HVM9-WC8J-MGRC is a high-severity incorrect authorization vulnerability in TShock (nuget), affecting versions >= 4.3.21, < 5.2.1. It is fixed in 5.2.1. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
2. Which versions of TShock are affected by GHSA-HVM9-WC8J-MGRC? TShock (nuget) versions >= 4.3.21, < 5.2.1 is affected.
3. Is there a fix for GHSA-HVM9-WC8J-MGRC? Yes. GHSA-HVM9-WC8J-MGRC is fixed in 5.2.1. Upgrade to this version or later.
4. Is GHSA-HVM9-WC8J-MGRC exploitable, and should I be worried? Whether GHSA-HVM9-WC8J-MGRC is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether GHSA-HVM9-WC8J-MGRC is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix GHSA-HVM9-WC8J-MGRC? Upgrade TShock to 5.2.1 or later.

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