CVE-2026-54738

Summary

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 Software

Weaknesses

• CWE-799: CWE-799: Improper Control of Interaction Frequency

References

• https://github.com/LemmyNet/lemmy/security/advisories/GHSA-2hrg-7x4g-9vpg
• https://github.com/LemmyNet/lemmy/pull/6574
• https://github.com/LemmyNet/lemmy/pull/6575
• https://github.com/LemmyNet/lemmy/commit/41513c89ceecee719bff05acfe613e3b1e85f23c
• https://github.com/LemmyNet/lemmy/commit/8b5b2aa78417b53ff3622c01f5bed2f1590f3b82
• https://github.com/LemmyNet/lemmy/releases/tag/0.19.19
• https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-beta.1
• https://join-lemmy.org/news/2026-06-09_-_Lemmy_Release_v0.19.19

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