CVE-2026-47777
HighCVSS 7.5Exploitation Probability (EPSS)
Low risk6th percentile — higher than 6% of all known CVEs
Summary
In Mastodon, versions with a missing condition in the check for remote accounts' consent to be featured in a remote Collection allow attackers to bypass this check and fake consent. This can lead to a situation where an account appears to be allowed in a Collection when it actually is not.
Risk Assessment
The organization may be exposed to false representation of accounts in Collections, which can lead to loss of user trust and privacy breaches.
Recommendation
It is recommended to update to version 4.6.0-beta.1 to mitigate this vulnerability and to disable the experimental 'Collections' feature if it is not necessary.
Original NVD description (English source)
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.