CVE-2026-54738: Lemmynet Lemmy

Medium severity, CVSS 6.5. EPSS: 0.6% chance of exploitation in the next 30 days.

Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-beta.1, actix-web ConnectionInfo::realip_remote_addr reads the first value of X-Forwarded-For as the client address used by raw_ip_key in crates/utils/src/rate_limit/mod.rs. Lemmy's bundled docker/nginx.conf uses $proxy_add_x_forwarded_for instead of $remote_addr, which appends the real client address to an X-Forwarded-For value supplied by the client. An unauthenticated attacker can therefore place a different spoofed address first on each request and receive a new rate-limit bucket, bypassing limits on POST /api/v4/account/auth/register, POST /api/v4/account/auth/login, POST /api/v4/post, POST /api/v4/comment, GET /api/v4/search, POST /api/v4/image, and POST /api/v4/account/import_settings. This permits excessive account creation, brute-force attempts, spam, scraping, uploads, and repeated imports. This issue is fixed in versions 0.19.19 and 1.0.0-beta.1.

Affected products

• Lemmynet Lemmy: before 0.19.19 (fixed in 0.19.19); from 1.0.0-alpha.5, before 1.0.0-beta.1 (fixed in 1.0.0-beta.1)

Published 2026-08-19. Last modified 2026-09-09.