CVE-2026-42180

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{"affected": [{"affectedData": [{"product": "lemmy", "vendor": "LemmyNet", "versions": [{"status": "affected", "version": "< 0.19.18"}]}], "source": "security-advisories@github.com"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}, {"lang": "es", "value": "Lemmy es un agregador de enlaces y un foro para el fediverso. Antes de la versi\u00f3n 0.19.18, Lemmy permite a un usuario autenticado con privilegios bajos crear una publicaci\u00f3n de enlace a trav\u00e9s de POST /API/v3/post. Cuando se crea una publicaci\u00f3n en una comunidad p\u00fablica, el backend env\u00eda asincr\u00f3nicamente una Webmention al objetivo de enlace controlado por el atacante. La URL enviada se verifica en cuanto a sintaxis y esquema, pero la ruta de c\u00f3digo auditada no rechaza destinos de loopback, privados o de enlace local antes de que se emita la solicitud de Webmention. Esto permite a un usuario normal activar solicitudes HTTP del lado del servidor hacia servicios internos. Este problema ha sido parcheado en la versi\u00f3n 0.19.18."}], "id": "CVE-2026-42180", "lastModified": "2026-10-26T18:10:00.173", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 6.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 3.4, "source": "security-advisories@github.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-42180", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-05-13T17:17:59.971593Z", "version": "2.0.3"}}]}, "published": "2026-05-08T20:16:31.023", "references": [{"source": "security-advisories@github.com", "url": "https://github.com/LemmyNet/lemmy/releases/tag/0.19.18"}, {"source": "security-advisories@github.com", "url": "https://github.com/LemmyNet/lemmy/security/advisories/GHSA-3jvj-v6w2-h948"}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "url": "https://github.com/LemmyNet/lemmy/security/advisories/GHSA-3jvj-v6w2-h948"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Deferred", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-918"}], "source": "security-advisories@github.com", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,0.19.18)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "lemmy", "source": "cna", "vendor": "LemmyNet"}, "product": "lemmy", "vendor": "lemmynet"}], "created": "2026-05-08T22:00:15.884226+00:00", "updated": "2026-05-08T22:30:18.071220+00:00", "vendors": ["lemmynet", "lemmynet$PRODUCT$lemmy"]}