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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-54738
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-19 21:16:58 UTC
Updated2026-08-21 22:16:40 UTC
DescriptionLemmy 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.

Risk And Classification

Primary CVSS: v3.1 6.5 MEDIUM from [email protected]

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

EPSS: 0.004280000 probability, percentile 0.359690000 (date 2026-08-21)

Problem Types: CWE-799 | CWE-799 CWE-799: Improper Control of Interaction Frequency

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
3.1CNADECLARED6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
Low

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA LemmyNet Lemmy affected < 0.19.19 Not specified
CNA LemmyNet Lemmy affected >= 1.0.0-alpha.5, < 1.0.0-beta.1 Not specified

References

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