CVE-2026-54740

Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-alpha.18, a lower-ranked remote moderator can remove a higher-ranked moderator by sending a signed ActivityPub Remove activity to the target instance. The local API uses LocalUser::ishighermodoradmincheck to enforc...

CVE-2026-54740

In Lemmy versions prior to 0.19.19 and 1.0.0-alpha.18, the federated ActivityPub handler CollectionRemove::receive in crates/apub/activities/src/community/collection_remove.rs omits the rank check (is_higher_mod_or_admin_check) enforced by the local API, allowing any signed ActivityPub Remove act...

CVE-2026-54740 Lemmy: Lower-ranked federated moderator can remove higher-ranked moderators

Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-alpha.18, a lower-ranked remote moderator can remove a higher-ranked moderator by sending a signed ActivityPub Remove activity to the target instance. The local API uses LocalUser::ishighermodoradmincheck to enforc...

CVE-2026-54740 Lemmy: Lower-ranked federated moderator can remove higher-ranked moderators

Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-alpha.18, a lower-ranked remote moderator can remove a higher-ranked moderator by sending a signed ActivityPub Remove activity to the target instance. The local API uses LocalUser::ishighermodoradmincheck to enforc...

EUVD-2026-62844

Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-alpha.18, a lower-ranked remote moderator can remove a higher-ranked moderator by sending a signed ActivityPub Remove activity to the target instance. The local API uses LocalUser::ishighermodoradmincheck to enforc...

CVE-2026-54742 Lemmy: `CollectionAdd::Featured` does not check the post is in the community

Lemmy is a link aggregator and forum for the fediverse. From 0.19.18 until 0.19.19 and 1.0.0-alpha.20, a community moderator can feature or unfeature posts in other communities through federated CollectionAdd and CollectionRemove activities using CollectionType::Featured. After verifymodaction...

PT-2026-78675

Name of the Vulnerable Software and Affected Versions Lemmy versions prior to 0.19.19 Lemmy versions prior to 1.0.0-alpha.18 Description A lower-ranked remote moderator can remove a higher-ranked moderator by sending a signed ActivityPub Remove activity to the target instance. While the local API...

PT-2026-78677

Name of the Vulnerable Software and Affected Versions Lemmy versions 0.19.18 through 0.19.18 Lemmy versions 1.0.0-alpha.1 through 1.0.0-alpha.19 Description A community moderator can feature or unfeature posts belonging to other communities. This occurs during federated CollectionAdd and...

BIT-MASTODON-2026-72916 Mastodon: SSRF Protection Bypass via IPv4-compatible IPv6 Addresses

Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.4.21, 4.5.14, 4.6.4, and 4.7.0, PrivateAddressCheck.privateaddress? in app/lib/privateaddresscheck.rb normalized IPv4-mapped IPv6 addresses but did not recognize IPv4-compatible IPv6 addresses with...

BIT-MASTODON-2026-72914 Mastodon: Exhausting data by an unauthenticated request to the admin retention API

Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.4.21, 4.5.14, 4.6.4, and 4.7.0, the administrative statistics endpoints handled by Api::V1::Admin::MeasuresController and Api::V1::Admin::RetentionController checked authorization only after beginning expensive...

CVE-2026-73038

NodeBB before 4.15.0 contains a stored cross-site scripting vulnerability in the renderEmoji function that fails to escape tag.icon.url and tag.name attributes. Attackers can deliver malicious ActivityPub Create/Note objects with crafted emoji tags to inject arbitrary HTML and JavaScript into...

EUVD-2026-58226

NodeBB before 4.15.0 contains a stored cross-site scripting vulnerability in the renderEmoji function that fails to escape tag.icon.url and tag.name attributes. Attackers can deliver malicious ActivityPub Create/Note objects with crafted emoji tags to inject arbitrary HTML and JavaScript into...

CVE-2026-73038 NodeBB < 4.15.0 Stored XSS via ActivityPub emoji tag.icon.url and tag.name

NodeBB before 4.15.0 contains a stored cross-site scripting vulnerability in the renderEmoji function that fails to escape tag.icon.url and tag.name attributes. Attackers can deliver malicious ActivityPub Create/Note objects with crafted emoji tags to inject arbitrary HTML and JavaScript into...

CVE-2026-73038 NodeBB < 4.15.0 Stored XSS via ActivityPub emoji tag.icon.url and tag.name

NodeBB before 4.15.0 contains a stored cross-site scripting vulnerability in the renderEmoji function that fails to escape tag.icon.url and tag.name attributes. Attackers can deliver malicious ActivityPub Create/Note objects with crafted emoji tags to inject arbitrary HTML and JavaScript into...

CVE-2026-73038

NodeBB before 4.15.0 contains a stored cross-site scripting vulnerability in the renderEmoji function that fails to escape tag.icon.url and tag.name attributes. Attackers can deliver malicious ActivityPub Create/Note objects with crafted emoji tags to inject arbitrary HTML and JavaScript into...

CVE-2026-73038

NodeBB before 4.15.0 contains a stored XSS in the renderEmoji function due to failed escaping of tag.icon.url and tag.name within ActivityPub emoji tags. Attackers can send crafted Create/Note objects to inject HTML/JS into stored post content, leading to code execution in viewers’ browsers. Impa...

CVE-2026-73211

PeerTube is an ActivityPub-federated video streaming platform. Prior to 8.1.6, ActorFollowModel.updateScore interpolates the attacker-controlled ActivityPub actor inboxUrl into an SQL query, allowing an unauthenticated remote server to read and write PeerTube database tables, including...

CVE-2026-73090

PeerTube is an ActivityPub-federated video streaming platform. Prior to 8.2.2, processUpdateActivity and processUpdateVideo accept an ActivityPub Update containing a Video object without verifying that byActor.url is authorized for the host in videoObject.id, allowing a malicious federated server...

CVE-2026-73211

PeerTube (ActivityPub-federated video platform) pre-8.1.6 is affected by an unauthenticated remote SQL injection in ActorFollowModel.updateScore(), where the attacker-controlled inboxUrl is interpolated into an SQL query. This allows reading and writing of database tables, including oAuthToken.ac...

CVE-2026-73211 PeerTube: Unauthenticated remote SQL injection in ActorFollowModel.updateScore()

PeerTube is an ActivityPub-federated video streaming platform. Prior to 8.1.6, ActorFollowModel.updateScore interpolates the attacker-controlled ActivityPub actor inboxUrl into an SQL query, allowing an unauthenticated remote server to read and write PeerTube database tables, including...