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CVE-2026-54738— Lemmy: Rate limit bypass via X-Forwarded-For header spoofing in actix-web ConnectionInfo

Quick assessment

Affected
LemmyNet lemmy
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

LemmyNet lemmy是LemmyNet组织的一个去中心化的链接聚合与讨论社区平台。 LemmyNet lemmy 0.19.19之前版本和1.0.0-alpha.5至1.0.0-beta.1之前版本存在资源管理错误漏洞，该漏洞源于对X-Forwarded-For标头处理不当，允许未认证攻击者通过伪造客户端地址绕过速率限制，可能导致过度账户创建、暴力破解尝试、垃圾信息、爬取、上传和重复导入。

CVSS 6.5 · Medium EPSS 0.43% · P36

Affected Version Matrix 2

VendorProduct Version RangeStatus
LemmyNet lemmy < 0.19.19 affected
>= 1.0.0-alpha.5, < 1.0.0-beta.1 affected
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I. Basic Information for CVE-2026-54738

Vulnerability Information
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Vulnerability Title
Lemmy: Rate limit bypass via X-Forwarded-For header spoofing in actix-web ConnectionInfo
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
交互频率的控制不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
LemmyNet lemmy 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
LemmyNet lemmy是LemmyNet组织的一个去中心化的链接聚合与讨论社区平台。 LemmyNet lemmy 0.19.19之前版本和1.0.0-alpha.5至1.0.0-beta.1之前版本存在资源管理错误漏洞，该漏洞源于对X-Forwarded-For标头处理不当，允许未认证攻击者通过伪造客户端地址绕过速率限制，可能导致过度账户创建、暴力破解尝试、垃圾信息、爬取、上传和重复导入。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
LemmyNet lemmy < 0.19.19 -

II. Public POCs for CVE-2026-54738

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III. Intelligence Information for CVE-2026-54738

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Patches & Fixes for CVE-2026-54738 (4)

Vendor Advisories for CVE-2026-54738 (1)

Vendor Pages for CVE-2026-54738 (3)

Same Patch Batch · LemmyNet · 2026-08-19 · 6 CVEs total

CVE-2026-54739 6.9 MEDIUM Lemmy: Login Endpoint User Enumeration via HTTP Response Code Differential
CVE-2026-54740 6.5 MEDIUM Lemmy: Lower-ranked federated moderator can remove higher-ranked moderators
CVE-2026-54743 6.4 MEDIUM Lemmy: Stored XSS via markdown image alt-text in lemmy-ui html5-embed
CVE-2026-54741 5.3 MEDIUM Lemmy: Blocked users can edit private messages sent before the block
CVE-2026-54742 5.1 MEDIUM Lemmy: `CollectionAdd::Featured` does not check the post is in the community

IV. Related Vulnerabilities

Same product: lemmy
Same vendor: LemmyNet
Same weakness: CWE-799

V. Comments for CVE-2026-54738

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