| Package | Affected versions | Patched versions |
|---|---|---|
| misskey | = 13.0.0≥ 13.1.0, < 2025.12.0 | 2025.12.0 |
| misskey-js | ≥ 2025.9.1, < 2025.12.0-alpha.2 | 2025.12.0-alpha.2 |
When using an untrusted reverse proxy or not using a reverse proxy at all, attackers can bypass IP rate limiting by adding a forged X-Forwarded-For header. Starting with version 2025.9.1, an option (trustProxy) has been added in config file to prevent this from happening. However, it is initialized with an insecure default value before version 2025.12.0, making it still vulnerable if the configuration is not set correctly.
If you are running Misskey with a trusted reverse proxy, you should not be affected by this vulnerability.
trustProxy: false in config file.trustProxy to false. If you are using trusted reverse proxy and not remember you manually overrided this value, please take time to check your config for optimal behavior.Fastify recommend not trusting X-Forwarded-For IPs Due to misconfiguration in https://github.com/misskey-dev/misskey/blob/develop/packages/backend/src/server/api/SigninApiService.ts#L94 attacks can spoof their IPs.
POST /api/signin-flow HTTP/1.1
Host: misskey.localhost:3123
Content-Length: 45
Content-Type: application/json
Connection: keep-alive
X-Forwarded-For: 127.1.1.31, 1.1.1.12
{"username":"admin",
"password":"password"}
An attacker can brute force accounts bypassing rate limiting protection.
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