{"cve":"CVE-2026-42180","nvd":{"published":"2026-05-08T20:16:31.023","modified":"2026-10-26T18:10:00.173","status":"Deferred","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L","score":6.3},"cwes":["CWE-918"],"references":["https://github.com/LemmyNet/lemmy/releases/tag/0.19.18","https://github.com/LemmyNet/lemmy/security/advisories/GHSA-3jvj-v6w2-h948","https://github.com/LemmyNet/lemmy/security/advisories/GHSA-3jvj-v6w2-h948"],"products":[],"source":"nvd","synced_at":"2026-10-26T18:27:13.530666824+00:00"},"epss":{"cve":"CVE-2026-42180","score":0.00184,"percentile":0.07863,"date":"2026-10-26"},"kev":null,"osv":[{"id":"GHSA-3jvj-v6w2-h948","url":"https://osv.dev/vulnerability/GHSA-3jvj-v6w2-h948","summary":"Lemmy has SSRF in /api/v3/post via Webmention dispatch","modified":"2026-05-13T13:56:07.079912Z","packages":[{"ecosystem":"crates.io","name":"lemmy_api_common","purl":"pkg:cargo/lemmy_api_common","ranges":["<0.19.18"],"fixed":["0.19.18"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}