CVE-2026-54740

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 77% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.5Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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::is_higher_mod_or_admin_check to enforce moderator rank, but CollectionRemove::verify in crates/apub/activities/src/community/collection_remove.rs only calls verify_mod_action. CollectionRemove::receive dereferences self.object as an ApubPerson, creates a CommunityModeratorForm, and calls CommunityActions::leave without checking that the actor outranks the moderator identified by the object field. In communities with federated moderators, a junior moderator can therefore strip senior moderators from the community moderator list even though the local API rejects the same action. This issue is fixed in versions 0.19.19 and 1.0.0-alpha.18.

CVSS v3
6.5
EG Score
6.5(medium)
EG Risk
45(Track)
EG Risk 45/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity65% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
23%
KEV
Not listed

Published

August 19, 2026

Last Modified

August 20, 2026

Advisory Details (8)

Auto-updated Aug 19, 2026
🔬 Proof of concept available. Patch available. Sources: github, github_pr, github_commit, github_release.
generic

2026-06-09 - Lemmy Release v0.19.19

https://join-lemmy.org/news/2026-06-09_-_Lemmy_Release_v0.19.19
github_release Patch Available

1.0.0-alpha.18

Patch available: LemmyNet/lemmy 1.0.0-alpha.18 (pre-release)

https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-alpha.18
github_release Patch Available

0.19.19

Patch available: LemmyNet/lemmy 0.19.19

https://github.com/LemmyNet/lemmy/releases/tag/0.19.19
github_commit Patch Available

commit ede1d348344c (LemmyNet/lemmy)

Patch available: LemmyNet/lemmy 0.19.19 (contains commit ede1d348344c)

https://github.com/LemmyNet/lemmy/commit/ede1d348344ca2027fd1bc6a0cab25575c0c3a4c
github_commit Patch Available

commit d127e714a66f (LemmyNet/lemmy)

Patch available: LemmyNet/lemmy 1.0.0-alpha.18 (contains commit d127e714a66f)

https://github.com/LemmyNet/lemmy/commit/d127e714a66f34f6b9c8ea15f20097ac907cdf28
github_pr Patch Available

[0.19] Check mod hierarchy when removing mod via federation

Patch available: LemmyNet/lemmy 0.19.19 (PR #6478 merged 2026-04-30)

https://github.com/LemmyNet/lemmy/pull/6478
github_pr Patch Available

Check mod hierarchy when removing mod via federation

Patch available: LemmyNet/lemmy 1.0.0-alpha.18 (PR #6475 merged 2026-04-29)

https://github.com/LemmyNet/lemmy/pull/6475
github Patch Available🟡 PoC Available

Lower-ranked federated moderator can remove higher-ranked moderators · Advisory · LemmyNet/lemmy · GitHub

https://github.com/LemmyNet/lemmy/security/advisories/GHSA-xmpx-2j2f-c7g7

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 22× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-30 01:22 UTCEPSS rescore
  2. 2026-08-29 03:10 UTCEG score recompute
  3. 2026-08-28 21:41 UTCEPSS rescore
  4. 2026-08-28 05:02 UTCEG score recompute
  5. 2026-08-27 14:25 UTCEPSS rescore
  6. 2026-08-27 06:55 UTCEG score recompute
  7. 2026-08-26 14:46 UTCEPSS rescore
  8. 2026-08-26 08:50 UTCEG score recompute
  9. 2026-08-25 13:49 UTCEPSS rescore
  10. 2026-08-25 10:44 UTCEG score recompute
  11. 2026-08-24 12:39 UTCEG score recompute
  12. 2026-08-23 14:34 UTCEG score recompute
  13. 2026-08-23 00:19 UTCEPSS rescore
  14. 2026-08-22 16:30 UTCEG score recompute
  15. 2026-08-21 23:49 UTCEPSS rescore
  16. 2026-08-21 18:25 UTCEG score recompute
  17. 2026-08-20 22:55 UTCEPSS rescore
  18. 2026-08-20 20:20 UTCEG score recompute
  19. 2026-08-20 20:02 UTCEG score recompute
  20. 2026-08-19 21:20 UTCEG score recompute
  21. 2026-08-19 20:28 UTCEG score recompute
  22. 2026-08-19 20:27 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-54740?
CVE-2026-54740 is a medium vulnerability published on August 19, 2026. 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 enforce…
When was CVE-2026-54740 disclosed?
CVE-2026-54740 was first published in the National Vulnerability Database on August 19, 2026, with the most recent update on August 20, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-54740 actively exploited?
CVE-2026-54740 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 76.6% of all scored CVEs.
What is the CVSS score of CVE-2026-54740?
CVE-2026-54740 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-54740?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-54740, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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