CVE-2026-547396.9MediumCWE-204

CVE-2026-54739: Lemmy: Login Endpoint User Enumeration via HTTP Response Code Differential

LemmyNet · lemmy

Affected: LemmyNet · Exploitation: unlikely (under 1%)

Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.

0.6%probability of exploitation in the next 30 days

48th percentile

050100

Higher than 48% of scored CVEs

6.9MediumCVSS 4.0

LowMediumHighCrit.

DescriptionCVE.org

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.

Affected products1

From the CVE record. A product or version that is not listed is unknown, not unaffected.

LemmyNet · lemmy< 0.19.19; >= 1.0.0-alpha.0, < 1.0.0-beta.1

On the Atlas

Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.

Open the Atlas

Exploitation: Unlikely (under 1%). EPSS under 1%, or no score yet.
CISA KEV: Not listed
Public check: No public nuclei template
Weakness: Observable Response Discrepancy · Information Disclosure
Vendor: LemmyNet
Published: August 2026
Band: Unlikely (under 1%), August 2026

CoverageNo articles yet

No CyberSIXT article names CVE-2026-54739 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.