CVE-2026-54738 PUBLISHED

Lemmy: Rate limit bypass via X-Forwarded-For header spoofing in actix-web ConnectionInfo

Assigner: GitHub_M
Reserved: 15.06.2026 Published: 19.08.2026 Updated: 19.08.2026

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.

Metrics

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
CVSS Score: 6.5

Product Status

Vendor LemmyNet
Product lemmy
Versions
  • Version < 0.19.19 is affected
  • Version >= 1.0.0-alpha.5, < 1.0.0-beta.1 is affected

References

Problem Types

  • CWE-799: Improper Control of Interaction Frequency CWE