CVE-2024-37903: Joinmastodon Mastodon

High severity, CVSS 8.2. EPSS: 0.5% chance of exploitation in the next 30 days.

Mastodon is a self-hosted, federated microblogging platform. Starting in version 2.6.0 and prior to versions 4.1.18 and 4.2.10, by crafting specific activities, an attacker can extend the audience of a post they do not own to other Mastodon users on a target server, thus gaining access to the contents of a post not intended for them. Versions 4.1.18 and 4.2.10 contain a patch for this issue.

Affected products

• Joinmastodon Mastodon: from 2.6.0, before 4.1.18 (fixed in 4.1.18); from 4.2.0, before 4.2.10 (fixed in 4.2.10)

Published 2024-07-05. Last modified 2026-06-17.