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: 0.6% (46th percentile of EPSS-scored CVEs). 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
6.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.6%CVSS: 6.9Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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
6.9MEDIUMmedium confidence
EG Risk
46
EG Risk 46/100CISA SSVC

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%
Exploitation1% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.6%
EPSS %ILE
46th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 19, 2026

Last Modified

September 9, 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
githubMentions a patch (unverified)🟡 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 11× in last 7d / 51× 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. 2026-10-09 20:07 UTCEPSS rescore
  2. 2026-10-08 17:12 UTCEPSS rescore
  3. 2026-10-08 06:36 UTCEG score recompute
  4. 2026-10-07 23:48 UTCEPSS rescore
  5. 2026-10-07 02:13 UTCEG score recompute
  6. 2026-10-06 15:18 UTCEPSS rescore
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  8. 2026-10-05 17:43 UTCEPSS rescore
  9. 2026-10-05 01:57 UTCEG score recompute
  10. 2026-10-04 23:22 UTCEPSS rescore
  11. 2026-10-04 03:35 UTCEG score recompute
  12. 2026-10-03 14:26 UTCEPSS rescore
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  14. 2026-10-02 17:56 UTCEPSS rescore
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  16. 2026-10-01 19:50 UTCEPSS rescore
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  18. 2026-09-30 15:03 UTCEPSS rescore
  19. 2026-09-30 08:37 UTCEG score recompute
  20. 2026-09-29 15:22 UTCEPSS rescore
  21. 2026-09-29 02:41 UTCEG score recompute
  22. 2026-09-28 13:51 UTCEPSS rescore
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  24. 2026-09-27 13:48 UTCEPSS rescore
  25. 2026-09-27 05:57 UTCEG score recompute
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  1. 2026-09-26 15:59 UTCEPSS rescore
  2. 2026-09-25 00:48 UTCEG score recompute
  3. 2026-09-24 14:04 UTCEPSS rescore
  4. 2026-09-23 22:17 UTCEG score recompute
  5. 2026-09-23 17:54 UTCEPSS rescore
  6. 2026-09-22 23:56 UTCEG score recompute
  7. 2026-09-22 01:33 UTCEG score recompute
  8. 2026-09-21 03:11 UTCEG score recompute
  9. 2026-09-20 20:16 UTCEPSS rescore
  10. 2026-09-20 04:41 UTCEG score recompute
  11. 2026-09-19 06:17 UTCEG score recompute
  12. 2026-09-18 19:28 UTCEPSS rescore
  13. 2026-09-18 07:54 UTCEG score recompute
  14. 2026-09-17 19:31 UTCEPSS rescore
  15. 2026-09-17 09:31 UTCEG score recompute
  16. 2026-09-16 14:08 UTCEPSS rescore
  17. 2026-09-16 11:09 UTCEG score recompute
  18. 2026-09-16 05:15 UTCEPSS rescore
  19. 2026-09-15 12:47 UTCEG score recompute
  20. 2026-09-15 03:11 UTCEPSS rescore
  21. 2026-09-14 14:25 UTCEG score recompute
  22. 2026-09-13 16:47 UTCEPSS rescore
  23. 2026-09-12 17:41 UTCEG score recompute
  24. 2026-09-11 19:19 UTCEG score recompute
  25. 2026-09-11 14:53 UTCEPSS rescore
  26. 2026-09-10 20:57 UTCEG score recompute
  27. 2026-09-10 09:35 UTCEPSS rescore
  28. 2026-09-09 02:29 UTCEG score recompute
  29. 2026-09-08 22:01 UTCEPSS rescore
  30. 2026-09-07 19:03 UTCEG score recompute
  31. 2026-09-07 16:01 UTCEPSS rescore
  32. 2026-09-06 20:41 UTCEG score recompute
  33. 2026-09-06 13:47 UTCEPSS rescore
  34. 2026-09-05 22:18 UTCEG score recompute
  35. 2026-09-04 23:54 UTCEG score recompute
  36. 2026-09-04 05:06 UTCEPSS rescore
  37. 2026-09-03 01:21 UTCEG score recompute
  38. 2026-09-02 14:12 UTCEPSS rescore
  39. 2026-09-02 02:58 UTCEG score recompute
  40. 2026-09-01 13:54 UTCEPSS rescore
  41. 2026-09-01 04:40 UTCEPSS rescore
  42. 2026-08-31 06:10 UTCEG score recompute
  43. 2026-08-30 19:17 UTCEPSS rescore
  44. 2026-08-30 07:44 UTCEG score recompute
  45. 2026-08-30 01:22 UTCEPSS rescore
  46. 2026-08-29 09:22 UTCEG score recompute
  47. 2026-08-28 21:41 UTCEPSS rescore
  48. 2026-08-28 11:00 UTCEG score recompute
  49. 2026-08-27 14:25 UTCEPSS rescore
  50. 2026-08-27 12:37 UTCEG score recompute
  51. 2026-08-26 14:46 UTCEPSS rescore
  52. 2026-08-25 15:53 UTCEG score recompute
  53. 2026-08-25 13:49 UTCEPSS rescore
  54. 2026-08-24 17:32 UTCEG score recompute
  55. 2026-08-23 19:10 UTCEG score recompute
  56. 2026-08-23 00:19 UTCEPSS rescore
  57. 2026-08-22 20:48 UTCEG score recompute
  58. 2026-08-21 23:49 UTCEPSS rescore
  59. 2026-08-21 22:26 UTCEG score recompute
  60. 2026-08-21 22:00 UTCEG score recompute
  61. 2026-08-21 18:05 UTCEG score recompute
  62. 2026-08-20 22:55 UTCEPSS rescore
  63. 2026-08-19 21:20 UTCEG score recompute
  64. 2026-08-19 20:28 UTCEG score recompute
  65. 2026-08-19 20:27 UTCMITRE cvelistV5first tracked

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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 on August 19, 2026, with the most recent update on September 9, 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 0.6% probability of exploitation in the next 30 days (46th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-54739?
CVE-2026-54739 has a CVSS base score of 6.9 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-54739?
A fix for CVE-2026-54739 is available: update to the fixed version the vendor names in its advisory.

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