CVE-2026-42180 (GCVE-0-2026-42180)
Vulnerability from cvelistv5 – Published: 2026-05-08 19:29 – Updated: 2026-05-13 17:18
VLAI?
Title
Lemmy: SSRF in /api/v3/post via Webmention dispatch
Summary
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.
Severity ?
6.3 (Medium)
CWE
- CWE-918 - Server-Side Request Forgery (SSRF)
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/LemmyNet/lemmy/security/adviso… | x_refsource_CONFIRM |
| https://github.com/LemmyNet/lemmy/releases/tag/0.19.18 | x_refsource_MISC |
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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