CVE-2026-54739

UNKNOWN 0.0

Lemmy: Login Endpoint User Enumeration via HTTP Response Code Differential

CVSS Score

0.0

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-204
Vendor	lemmynet
Product	lemmy
Published	Aug 19, 2026

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Affected Versions

LemmyNet / lemmy

< 0.19.19 >= 1.0.0-alpha.0, < 1.0.0-beta.1

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/LemmyNet/lemmy/security/advisories/GHSA-xgg7-8hvq-8m65 github.com: https://github.com/LemmyNet/lemmy/pull/6531 github.com: https://github.com/LemmyNet/lemmy/pull/6535 github.com: https://github.com/LemmyNet/lemmy/commit/4d235a1b668b7dda6b73dbbc9ca289bb40acfa83 github.com: https://github.com/LemmyNet/lemmy/commit/59e968a5ac36d36d08a59028e2dbb92641536964 github.com: https://github.com/LemmyNet/lemmy/releases/tag/0.19.19 github.com: https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-beta.1 join-lemmy.org: https://join-lemmy.org/news/2026-06-09_-_Lemmy_Release_v0.19.19