CVE-2026-54742

5.1 MEDIUM 0.5% exploit odds Fix listed Auth & access

What it is

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.

At a glance

Exploitability: Can be exploited over the network with an admin-level account. Limited direct impact.
Exploit odds: 0.5% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-08-19 20:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-09-09 21:15 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.5% in the next 30 days (EPSS).
Severity: 5.1 MEDIUM (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-08-19 20:17 UTC
Last modified: 2026-09-09 21:15 UTC
Exploit probability: 0.5% · EPSS, next 30 days
Weakness: CWE-863 · Incorrect authorization
Record status: Deferred

Attack profile CVSS 4.0 · 5.1

Attack vector: Network
Complexity: Low
Attack requirements: None
Privileges needed: High
User interaction: None
Confidentiality: None
Integrity: Low
Availability: None

Raw vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-54742.md and follow it. Check whether this project is affected by CVE-2026-54742. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record