CVE-2026-54739

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

No CVSS.

References

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

Configurations

No configuration.

History

No history.

Information

Published : 2026-08-19 21:16

Updated : 2026-09-09 21:15

NVD link : CVE-2026-54739

Mitre link : CVE-2026-54739

CVE.ORG link : CVE-2026-54739

JSON object : View

Products Affected

No product.

CWE

CWE-204

Observable Response Discrepancy

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