CVE-2026-54739

MEDIUMPre-NVD 6.96.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 64% 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
Trending — 3 sources updated this week
6.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.9Exploit: None knownExposed: 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-beta.1, Lemmy's login endpoint in crates/api/api/src/local_user/login.rs returns different errors depending on whether the username_or_email value exists. LocalUserView::find_by_email_or_name propagates a NotFound response for an unknown account, while an existing account with a wrong password returns LemmyErrorType::IncorrectLogin. This observable response discrepancy, including HTTP 404 for a nonexistent account and HTTP 400 for an incorrect password on an existing account, allows an unauthenticated attacker to confirm registered usernames or email addresses and use the results for targeted credential attacks or social engineering. This issue is fixed in versions 0.19.19 and 1.0.0-beta.1.

CVSS v3
6.9
EG Score
6.9(medium)
EG Risk
46(Track)
EG Risk 46/100SSVC: 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
Severity69% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
36%
KEV
Not listed

Published

August 19, 2026

Last Modified

August 21, 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-beta.1

Patch available: LemmyNet/lemmy 1.0.0-beta.1 (pre-release)

https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-beta.1
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 59e968a5ac36 (LemmyNet/lemmy)

Patch available: LemmyNet/lemmy 0.19.19 (contains commit 59e968a5ac36)

https://github.com/LemmyNet/lemmy/commit/59e968a5ac36d36d08a59028e2dbb92641536964
github_commit Patch Available

commit 4d235a1b668b (LemmyNet/lemmy)

Patch available: LemmyNet/lemmy 1.0.0-beta.1 (contains commit 4d235a1b668b)

https://github.com/LemmyNet/lemmy/commit/4d235a1b668b7dda6b73dbbc9ca289bb40acfa83
github_pr Patch Available

[0.19] Prevent user enumeration via login endpoint

Patch available: LemmyNet/lemmy 0.19.19 (PR #6535 merged 2026-05-27)

https://github.com/LemmyNet/lemmy/pull/6535
github_pr Patch Available

Prevent user enumeration via login endpoint

Patch available: LemmyNet/lemmy 1.0.0-beta.1 (PR #6531 merged 2026-06-01)

https://github.com/LemmyNet/lemmy/pull/6531
github Patch Available🟡 PoC Available

Login Endpoint User Enumeration via HTTP Response Code Differential · Advisory · LemmyNet/lemmy · GitHub

https://github.com/LemmyNet/lemmy/security/advisories/GHSA-xgg7-8hvq-8m65

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 14× in last 7d / 14× 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. 2026-08-25 15:53 UTCEG score recompute
  2. 2026-08-25 13:49 UTCEPSS rescore
  3. 2026-08-24 17:32 UTCEG score recompute
  4. 2026-08-23 19:10 UTCEG score recompute
  5. 2026-08-23 00:19 UTCEPSS rescore
  6. 2026-08-22 20:48 UTCEG score recompute
  7. 2026-08-21 23:49 UTCEPSS rescore
  8. 2026-08-21 22:26 UTCEG score recompute
  9. 2026-08-21 22:00 UTCEG score recompute
  10. 2026-08-21 18:05 UTCEG score recompute
  11. 2026-08-20 22:55 UTCEPSS rescore
  12. 2026-08-19 21:20 UTCEG score recompute
  13. 2026-08-19 20:28 UTCEG score recompute
  14. 2026-08-19 20:27 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-54739?
CVE-2026-54739 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-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::findbyemailor_name propagates a NotFound response…
When was CVE-2026-54739 disclosed?
CVE-2026-54739 was first published in the National Vulnerability Database on August 19, 2026, with the most recent update on August 21, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-54739 actively exploited?
CVE-2026-54739 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 64.1% of all scored CVEs.
What is the CVSS score of CVE-2026-54739?
CVE-2026-54739 has a CVSS v3 base score of 6.9 (NVD).
How do I remediate CVE-2026-54739?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-54739, 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.

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