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CVE-2026-77164

Estado: AplazadaMedia (6.2)—

Circles' remote-instance signature verification fetches the attacker-supplied keyId URL before trust in the remote instance is established, and explicitly allows local/private addresses for this request, bypassing Nextcloud's core SSRF protections. The public, unauthenticated endpoints POST /apps/circles/event/ and POST /apps/circles/incoming/ reach this code path, allowing any unauthenticated user to force the server to issue a GET request to an internal address.

The response body of the internal request is never returned to the requester, so this is blind SSRF: an attacker can determine whether an internal service is reachable, but cannot read its response contents through this endpoint alone.

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

Inferido por reglas deterministas a partir del vector CVSS y la CWE. Solo orientativo.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Threat Intelligence ProgramSSL/TLS InspectionNetwork Intrusion PreventionFilter Network TrafficExecution PreventionApplication Isolation and Sandboxing

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Nextcloud — CirclesAI

CWE

Referencias

JSON original (NVD)

Mostrar
{
  "id": "CVE-2026-77164",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-77164",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-09-18T19:40:57.953385Z"
        }
      }
    ],
    "cvssMetricV30": [
      {
        "type": "Secondary",
        "source": "support@hackerone.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.0",
          "baseScore": 6.2,
          "attackVector": "LOCAL",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 2.5
      }
    ]
  },
  "affected": [
    {
      "source": "support@hackerone.com",
      "affectedData": [
        {
          "vendor": "Nextcloud",
          "product": "Server",
          "versions": [
            {
              "status": "affected",
              "version": "31.0.0",
              "versionType": "semver",
              "lessThanOrEqual": "32.0.0"
            }
          ],
          "defaultStatus": "unaffected"
        }
      ]
    }
  ],
  "published": "2026-09-18T02:17:07.510",
  "references": [
    {
      "url": "https://hackerone.com/reports/3303283",
      "source": "support@hackerone.com"
    }
  ],
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "support@hackerone.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-918"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Circles' remote-instance signature verification fetches the attacker-supplied keyId URL before trust in the remote instance is established, and explicitly allows local/private addresses for this request, bypassing Nextcloud's core SSRF protections. The public, unauthenticated endpoints POST /apps/circles/event/ and POST /apps/circles/incoming/ reach this code path, allowing any unauthenticated user to force the server to issue a GET request to an internal address.\n\nThe response body of the internal request is never returned to the requester, so this is blind SSRF: an attacker can determine whether an internal service is reachable, but cannot read its response contents through this endpoint alone."
    }
  ],
  "lastModified": "2026-09-18T20:17:22.273",
  "sourceIdentifier": "support@hackerone.com"
}