GHSA-MHGJ-JXXF-GXJ9

Vulnerability from github – Published: 2026-05-28 15:39 – Updated: 2026-05-28 15:39
VLAI
Details

Roundcube's HTML sanitization path for message rendering allows loopback, localhost, RFC1918, link-local, and ULA URLs even when remote content loading is disabled. A remote attacker can send an HTML email that causes the victim's browser to issue requests to local or private-network services simply by opening the message preview.

Severity
4.7 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N
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{
  "affected": [],
  "aliases": [
    "CVE-2026-9818"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-184"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-28T13:16:25Z",
    "severity": "MODERATE"
  },
  "details": "Roundcube\u0027s HTML sanitization path for message rendering allows loopback, localhost, RFC1918, link-local, and ULA URLs even when remote content loading is disabled. A remote attacker can send an HTML email that causes the victim\u0027s browser to issue requests to local or private-network services simply by opening the message preview.",
  "id": "GHSA-mhgj-jxxf-gxj9",
  "modified": "2026-05-28T15:39:50Z",
  "published": "2026-05-28T15:39:50Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-9818"
    },
    {
      "type": "WEB",
      "url": "https://github.com/roundcube/roundcubemail/commit/7b52353653a67e6073b97d70eb94047132b78556"
    },
    {
      "type": "WEB",
      "url": "https://github.com/roundcube/roundcubemail/commit/faf867432f51ebbe100382a70a9e3c042415ee1b"
    },
    {
      "type": "WEB",
      "url": "https://advisories.orangecyberdefense.com/advisories/163"
    },
    {
      "type": "WEB",
      "url": "https://github.com/roundcube/roundcubemail/releases/tag/1.6.16"
    },
    {
      "type": "WEB",
      "url": "https://github.com/roundcube/roundcubemail/releases/tag/1.7.1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ]
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.