CVE-2025-62605: 
Mastodon vulnerability analysis and mitigation

Mastodon, a free open-source social network server based on ActivityPub, was found to contain a vulnerability in versions prior to 4.4.8 and 4.5.0-beta.2. The vulnerability (CVE-2025-62605) was discovered on October 21, 2025, affecting the quote posts feature with quote controls that was introduced in Mastodon version 4.4 (GitHub Advisory).

The vulnerability stems from how Mastodon internally treats reblogs as statuses. Since reblogs were not specially treated in affected versions, attackers could bypass quote controls by reblogging any post and then quoting their own reblog. This would allow them to display a preview of the original post without proper authorization, circumventing the intended quote control restrictions. The vulnerability has been assigned a CVSS v3.1 base score of 4.3 (Medium) with a vector string of CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N (GitHub Advisory).

The vulnerability allows attackers to bypass quote controls and display previews of posts they weren't authorized to quote. This could potentially lead to unauthorized content sharing and compromise of content control mechanisms intended to protect user privacy and content distribution preferences (GitHub Advisory).

The vulnerability has been patched in Mastodon versions 4.4.8 and 4.5.0-beta.2. Users are advised to upgrade to these or newer versions to protect against this vulnerability (GitHub Release).