Misskey has a login rate limit bypass via spoofed X-Forwarded-For header

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.9 · 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 · score source

EPSS

• CVE-2025-66482: 0.34% estimated exploitation activity in the next 30 days; percentile 27.38 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary 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. Workaround If you are running Misskey with a trusted reverse proxy, you should not be affected by this vulnerability. - There is no workaround for the Misskey itself. Please update Misskey to the latest version or set up a trusted reverse proxy. - From v2025.9.1 to v2025.11.1, workaround is available. Set trustProxy: false in config file. - This is patched in v2025.12.0 by flipping default value of 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…

Published by the source

15 Dec 2025, 20:59 UTC

Last modified by the source

3 Feb 2026, 03:16 UTC

Source last checked

26 Oct 2026, 12:41 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-wwrj-3hvj-prpm

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-wwrj-3hvj-prpm

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# Patch Next advisory brief: CVE-2025-66482

Advisory: Misskey has a login rate limit bypass via spoofed X-Forwarded-For header
IDs: CVE-2025-66482, GHSA-wwrj-3hvj-prpm
Record: https://patchnext.com/advisories/cve-2025-66482 (revision 3, source checked 26 Oct 2026, 12:41 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: misskey-js 2025.12.0-alpha.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm misskey-js: affected >= 2025.9.1, < 2025.12.0-alpha.2; fixed in 2025.12.0-alpha.2

## Suggested inspection (read-only)
- `npm ls misskey-js --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on misskey-js.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-wwrj-3hvj-prpm (OSV record GHSA-wwrj-3hvj-prpm lists affected ranges: npm misskey-js >=2025.9.1 <2025.12.0-alpha.2 (fixed))
- Verified: https://github.com/advisories/GHSA-wwrj-3hvj-prpm (GitHub-reviewed advisory GHSA-wwrj-3hvj-prpm lists affected ranges: npm misskey-js >=2025.9.1 <2025.12.0-alpha.2)

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