CVE-2026-47777 Mastodon has a consent-check bypass in its remote Collections
Attackers can bypass consent checks to forge authorization for featuring accounts in remote Collections on Mastodon servers with experimental features enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-47777?
CVE-2026-47777 is a high-severity vulnerability in mastodon, published on 15 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Mastodon is a free, open-source social network server based on ActivityPub. In versions there is a missing condition in the check if remote accounts consented to be featured in a remote Collection could lead to attackers bypassing the check and faking consent. An attacker could forge the FeatureAuthorization object that is used to verify consent to be featured in a Collection and thus make it appear as if an account is allowed to be in a Collection when it actually is not. While the FeatureAuthorization must reside on the same domain as the object it is for, a check is missing to make sure said object is actually the same as in the Collection item. This allows an attacker to forge the authorization. Mastodon servers are affected only if running the main branch or nightly builds who have opted into testing the experimental "Collections" feature by setting the environment variable EXPERIMENTAL_FEATURES to a value including collections. This has been patched in version 4.6.0-beta.1.
Which versions are affected by CVE-2026-47777?
1 open source package ship an affected version, including mastodon.
| Package | Affected | Fixed in |
|---|---|---|
mastodon Bitnami | From nightly.2026-03-10.0 | 4.6.0 |
How do I fix CVE-2026-47777?
Upgrade mastodon to 4.6.0 or later.
Is CVE-2026-47777 being exploited?
There is no known exploitation of CVE-2026-47777 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as BIT-mastodon-2026-47777, GHSA-vg36-gxjg-2v46.