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CVE-2026-91134

Estado: AplazadaMedia (5.4)—

Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the Discourse post sanitizer allowed a stored cross-origin iframe to bypass the allowed_iframes prefix policy when the iframe src contained encoded userinfo. The sanitizer validated a decoded form differently from the stored iframe src, allowing the browser to interpret an attacker-controlled host while the allowlist check accepted the encoded URL as an allowed prefix. An authenticated user with posting privileges could persist the iframe in a post and cause attacker-controlled cross-origin content to be rendered. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.

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.

Explotación corregida por reglas (vector CVSS): era T1190

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Vulnerability ScanningThreat Intelligence ProgramRestrict File and Directory PermissionsPrivileged Account ManagementRemote Data StorageNetwork Segmentation

Tecnologías afectadas (1)

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

Discourse — DiscourseAI

CWE

Referencias

JSON original (NVD)

Mostrar
{
  "id": "CVE-2026-91134",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-91134",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-09-29T02:56:20.350456Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "security-advisories@github.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.4,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "LOW"
        },
        "impactScore": 2.5,
        "exploitabilityScore": 2.8
      }
    ]
  },
  "affected": [
    {
      "source": "security-advisories@github.com",
      "affectedData": [
        {
          "vendor": "discourse",
          "product": "discourse",
          "versions": [
            {
              "status": "affected",
              "version": "< 2026.8.0"
            },
            {
              "status": "affected",
              "version": ">= 2026.7.0-latest, < 2026.7.2"
            },
            {
              "status": "affected",
              "version": ">= 2026.6.0-latest, < 2026.6.3"
            },
            {
              "status": "affected",
              "version": ">= 2026.1.0-latest, < 2026.1.8"
            }
          ]
        }
      ]
    }
  ],
  "published": "2026-09-24T17:17:09.080",
  "references": [
    {
      "url": "https://github.com/discourse/discourse/commit/0a8015e6c7a5079981843721494d30c9a91f5415",
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/discourse/discourse/commit/1304b0c04f87534053b0d574ae5a9b9ba13dd590",
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/discourse/discourse/commit/bac7dd1201911851462483271b4567246fa1309d",
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/discourse/discourse/commit/fed3a58c48412ce7207b72a4629ddbc44482cd64",
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/discourse/discourse/pull/42882",
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/discourse/discourse/security/advisories/GHSA-54vw-chv3-wjpv",
      "source": "security-advisories@github.com"
    }
  ],
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "security-advisories@github.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-20"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the Discourse post sanitizer allowed a stored cross-origin iframe to bypass the allowed_iframes prefix policy when the iframe src contained encoded userinfo. The sanitizer validated a decoded form differently from the stored iframe src, allowing the browser to interpret an attacker-controlled host while the allowlist check accepted the encoded URL as an allowed prefix. An authenticated user with posting privileges could persist the iframe in a post and cause attacker-controlled cross-origin content to be rendered. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0."
    }
  ],
  "lastModified": "2026-09-29T03:17:21.580",
  "sourceIdentifier": "security-advisories@github.com"
}