cvedb.io
CVE-2026-25540
MEDIUM · CVSS 6.5
EPSS exploitation probability: 0%
Published 2026-02-04T22:16:00.233 · Last modified 2026-06-17T10:24:49.297

Summary

Mastodon is a free, open-source social network server based on ActivityPub. Prior to versions 4.3.19, 4.4.13, 4.5.6, Mastodon is vulnerable to web cache poisoning via `Rails.cache. When AUTHORIZED_FETCH is enabled, the ActivityPub endpoints for pinned posts and featured hashtags have contents that depend on the account that signed the HTTP request. However, these contents are stored in an internal cache and reused with no regards to the signing actor. As a result, an empty response generated for a blocked user account may be served to requests from legitimate non-blocked actors, or conversely, content intended for non-blocked actors may be returned to blocked actors. This issue has been patched in versions 4.3.19, 4.4.13, 4.5.6.

Affected products

joinmastodon — mastodon

Does this affect you?

Add your gear to cvedb and we'll alert you only when joinmastodon ships something exploited.

Check my exposure →

References

This product uses data from the NVD API but is not endorsed or certified by the NVD. Informational only; not professional security advice.