CVE-2026-42180— Lemmy: SSRF in /api/v3/post via Webmention dispatch
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I. Basic Information for CVE-2026-42180
Vulnerability Information
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Vulnerability Title
Lemmy: SSRF in /api/v3/post via Webmention dispatch
Source: NVD (National Vulnerability Database)
Vulnerability Description
Lemmy is a link aggregator and forum for the fediverse. Prior to version 0.19.18, Lemmy allows an authenticated low-privileged user to create a link post through POST /api/v3/post. When a post is created in a public community, the backend asynchronously sends a Webmention to the attacker-controlled link target. The submitted URL is checked for syntax and scheme, but the audited code path does not reject loopback, private, or link-local destinations before the Webmention request is issued. This lets a normal user trigger server-side HTTP requests toward internal services. This issue has been patched in version 0.19.18.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
Source: NVD (National Vulnerability Database)
Vulnerability Type
服务端请求伪造(SSRF)
Source: NVD (National Vulnerability Database)
Vulnerability Title
Lemmy 代码问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Lemmy是Lemmy开源的一款用于构建社交新闻聚合器和网络论坛的自由软件。 Lemmy 0.19.18之前版本存在代码问题漏洞，该漏洞源于创建链接帖子时未拒绝回环、私有或链路本地目标，可能导致服务端请求伪造。
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
II. Public POCs for CVE-2026-42180
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- Release 0.19.18 · LemmyNet/lemmy · GitHubx_refsource_MISC
- https://nvd.nist.gov/vuln/detail/CVE-2026-42180
IV. Related Vulnerabilities
Same product: lemmy
- CVE-2026-42181
Lemmy: SSRF and internal image disclosure in post link metad - CVE-2026-33693
Lemmy's Activitypub-Federation has SSRF via 0.0.0.0 bypass i - CVE-2026-29178
Lemmy: Unauthenticated SSRF via file_type query parameter in - CVE-2025-25194
Server-Side Request Forgery (SSRF) in activitypub_federation - CVE-2024-23649
Any authenticated user may obtain private message details fr
Same vendor: LemmyNet
- CVE-2026-42181
Lemmy: SSRF and internal image disclosure in post link metad - CVE-2026-33693
Lemmy's Activitypub-Federation has SSRF via 0.0.0.0 bypass i - CVE-2026-29178
Lemmy: Unauthenticated SSRF via file_type query parameter in - CVE-2025-25194
Server-Side Request Forgery (SSRF) in activitypub_federation - CVE-2024-23649
Any authenticated user may obtain private message details fr
Same weakness: CWE-918
- CVE-2026-44428
MCP Registry: GitHub OIDC tokens replayable across registry - CVE-2026-44430
MCP Registry: Unauthenticated SSRF: HTTP namespace verificat - CVE-2026-44661
python-utcp: SSRF via attacker-controlled OpenAPI servers[0] - CVE-2026-44589
nuxt-og-image SSRF — bypass of GHSA-pqhr-mp3f-hrpp / v6.2.5 - CVE-2026-44515
Nextcloud News: Authenticated blind SSRF via feed URL
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