CVE-2026-54742
Lemmy is a link aggregator and forum for the fediverse.
Overview
CVE-2026-54742 is a known-severity vulnerability. It was published on August 19, 2026.
Technical description
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 verify_mod_action authorizes the actor against self.community(), the receive handlers in crates/apub/activities/src/community/collection_add.rs and crates/apub/activities/src/community/collection_remove.rs dereference self.object as an ApubPost and update featured_community without verifying that post.community_id equals community.id. A moderator can therefore target an unrelated post owned by another community, push it into featured feeds and listings, or undo another community's legitimate curation decision. This issue is fixed in versions 0.19.19 and 1.0.0-alpha.20.
Remediation
Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
References
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Frequently asked questions
What is CVE-2026-54742?
CVE-2026-54742 is a known-severity vulnerability. It was published on August 19, 2026.
How severe is CVE-2026-54742?
CVSS score information is not yet available for this vulnerability. Check back as the CVE record is updated by NVD analysts.
How do I fix or remediate CVE-2026-54742?
Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-54742?
CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-54742 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.