CVE-2026-42180

{
  "id": "CVE-2026-42180",
  "sourceIdentifier": "[email protected]",
  "published": "2026-05-08T20:16:31.023",
  "lastModified": "2026-10-26T18:10:00.173",
  "vulnStatus": "Deferred",
  "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 versión 0.19.18, Lemmy permite a un usuario autenticado con privilegios bajos crear una publicación de enlace a través de POST /API/v3/post. Cuando se crea una publicación en una comunidad pública, el backend envía asincrónicamente 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 código 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 versión 0.19.18."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "LemmyNet",
          "product": "lemmy",
          "versions": [
            {
              "version": "< 0.19.18",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L",
          "baseScore": 6.3,
          "baseSeverity": "MEDIUM",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "LOW",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "availabilityImpact": "LOW"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 3.4
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-05-13T17:17:59.971593Z",
          "id": "CVE-2026-42180",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-918"
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://github.com/LemmyNet/lemmy/releases/tag/0.19.18",
      "source": "[email protected]"
    },
    {
      "url": "https://github.com/LemmyNet/lemmy/security/advisories/GHSA-3jvj-v6w2-h948",
      "source": "[email protected]"
    },
    {
      "url": "https://github.com/LemmyNet/lemmy/security/advisories/GHSA-3jvj-v6w2-h948",
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"
    }
  ]
}