---
id: CVE-2026-54739
title: Lemmy is a link aggregator and forum for the fediverse
summary: >-
  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.…
severity: none
cwe:
  - CWE-204
published: '2026-08-19'
updated: '2026-09-09'
sourceUpdated: '2026-09-09T21:15:59.613'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-54739'
references:
  - url: >-
      https://github.com/LemmyNet/lemmy/commit/4d235a1b668b7dda6b73dbbc9ca289bb40acfa83
    label: security-advisories@github.com
  - url: >-
      https://github.com/LemmyNet/lemmy/commit/59e968a5ac36d36d08a59028e2dbb92641536964
    label: security-advisories@github.com
  - url: 'https://github.com/LemmyNet/lemmy/pull/6531'
    label: security-advisories@github.com
  - url: 'https://github.com/LemmyNet/lemmy/pull/6535'
    label: security-advisories@github.com
  - url: 'https://github.com/LemmyNet/lemmy/releases/tag/0.19.19'
    label: security-advisories@github.com
  - url: 'https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-beta.1'
    label: security-advisories@github.com
  - url: 'https://github.com/LemmyNet/lemmy/security/advisories/GHSA-xgg7-8hvq-8m65'
    label: security-advisories@github.com
  - url: 'https://join-lemmy.org/news/2026-06-09_-_Lemmy_Release_v0.19.19'
    label: security-advisories@github.com
tags:
  - nvd
epss: 0.0059
epssPercentile: 0.45939
ingestedAt: '2026-09-09T21:22:45.544Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.