CVE-2026-54739

Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-beta.1, Lemmy's login endpoint in crates/api/api/src/localuser/login.rs returns different errors depending on whether the usernameoremail value exists. LocalUserView::findbyemailorname propagates a NotFound respons...

CVE-2026-54741

Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-alpha.18, Lemmy blocks new private messages from a sender after the recipient blocks that sender, but the edit path skips the same block check. createprivatemessage checks the recipient's block list with...

CVE-2026-54738

Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-beta.1, actix-web ConnectionInfo::realipremoteaddr reads the first value of X-Forwarded-For as the client address used by rawipkey in crates/utils/src/ratelimit/mod.rs. Lemmy's bundled docker/nginx.conf uses...

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-2026-54743

Lemmy is a link aggregator and forum for the fediverse. Prior to lemmy-ui 0.19.19-beta.1, LemmyNet/lemmy-ui renders Markdown in src/shared/markdown.ts for post bodies, comment bodies, private messages, and community and site sidebars through mdToHtml, which returns a raw html object that Inferno...

EUVD-2026-62850

Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-beta.1, actix-web ConnectionInfo::realipremoteaddr reads the first value of X-Forwarded-For as the client address used by rawipkey in crates/utils/src/ratelimit/mod.rs. Lemmy's bundled docker/nginx.conf uses...

CVE-2026-54738 Lemmy: Rate limit bypass via X-Forwarded-For header spoofing in actix-web ConnectionInfo

Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-beta.1, actix-web ConnectionInfo::realipremoteaddr reads the first value of X-Forwarded-For as the client address used by rawipkey in crates/utils/src/ratelimit/mod.rs. Lemmy's bundled docker/nginx.conf uses...

CVE-2026-54738

Lemmy , a fediverse link aggregator and forum, is vulnerable to rate limit bypass via X-Forwarded-For header spoofing in versions prior to 0.19.19 and 1.0.0-beta.1 . The root cause is that actix-web's ConnectionInfo::realip_remote_addr reads the first value of X-Forwarded-For as the client addres...

CVE-2026-54738 Lemmy: Rate limit bypass via X-Forwarded-For header spoofing in actix-web ConnectionInfo

Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-beta.1, actix-web ConnectionInfo::realipremoteaddr reads the first value of X-Forwarded-For as the client address used by rawipkey in crates/utils/src/ratelimit/mod.rs. Lemmy's bundled docker/nginx.conf uses...

CVE-2026-54743 Lemmy: Stored XSS via markdown image alt-text in lemmy-ui html5-embed

Lemmy is a link aggregator and forum for the fediverse. Prior to lemmy-ui 0.19.19-beta.1, LemmyNet/lemmy-ui renders Markdown in src/shared/markdown.ts for post bodies, comment bodies, private messages, and community and site sidebars through mdToHtml, which returns a raw html object that Inferno...

CVE-2026-54743 Lemmy: Stored XSS via markdown image alt-text in lemmy-ui html5-embed

Lemmy is a link aggregator and forum for the fediverse. Prior to lemmy-ui 0.19.19-beta.1, LemmyNet/lemmy-ui renders Markdown in src/shared/markdown.ts for post bodies, comment bodies, private messages, and community and site sidebars through mdToHtml, which returns a raw html object that Inferno...

EUVD-2026-62848

Lemmy is a link aggregator and forum for the fediverse. Prior to lemmy-ui 0.19.19-beta.1, LemmyNet/lemmy-ui renders Markdown in src/shared/markdown.ts for post bodies, comment bodies, private messages, and community and site sidebars through mdToHtml, which returns a raw html object that Inferno...

CVE-2026-54743

Lemmy (a fediverse link aggregator and forum) is affected by a stored XSS in lemmy-ui prior to version 0.19.19-beta.1 . The root cause lies in src/shared/markdown.ts, where mdToHtml returns a raw __html object injected by Inferno without a sanitizer pass. The [email protected] plugin,...

CVE-2026-54742

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...

CVE-2026-54739 Lemmy: Login Endpoint User Enumeration via HTTP Response Code Differential

Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-beta.1, Lemmy's login endpoint in crates/api/api/src/localuser/login.rs returns different errors depending on whether the usernameoremail value exists. LocalUserView::findbyemailorname propagates a NotFound respons...

CVE-2026-54739

In Lemmy versions before 0.19.19 and 1.0.0-beta.1, the login endpoint returns HTTP 404 for nonexistent accounts and HTTP 400 for wrong passwords on existing accounts, enabling unauthenticated user/email enumeration. No in-the-wild exploitation is reported. Upgrade to 0.19.19 or 1.0.0-beta.1.

CVE-2026-54739 Lemmy: Login Endpoint User Enumeration via HTTP Response Code Differential

Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-beta.1, Lemmy's login endpoint in crates/api/api/src/localuser/login.rs returns different errors depending on whether the usernameoremail value exists. LocalUserView::findbyemailorname propagates a NotFound respons...

EUVD-2026-62847

Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-beta.1, Lemmy's login endpoint in crates/api/api/src/localuser/login.rs returns different errors depending on whether the usernameoremail value exists. LocalUserView::findbyemailorname propagates a NotFound respons...

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

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...