Zimbra Collaboration Suite Briefcase CSS Sanitization Bypass via Non-ASCII Stylesheet Characters

{
  "id": "d311647856cb970913fe852012d6fb072d79fbe31b03fa949ad3972fb5c71852",
  "url": "https://www.cve.org/CVERecord?id=CVE-2026-93633",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Zimbra Collaboration Suite Briefcase CSS Sanitization Bypass via Non-ASCII Stylesheet Characters",
    "summary": "A CSS sanitization vulnerability in Zimbra Collaboration Suite (ZCS) allows an authenticated user with Briefcase access to publish a document that displays attacker-controlled content under the Zimbra origin. When processing a stylesheet containing non-ASCII characters, DefangFilter appends the final ASCII segment without sanitizing it. HTML stored as application/x-zimbra-doc can therefore retain CSS URL references that the normal sanitizer removes. An attacker can share a crafted document that loads external resources and displays a credential-collection form using Zimbra's own visual assets. Exploitation requires the victim to open the document in a browser that renders the content type inline; credential theft additionally requires form submission. ZCS 10.1.16 and 10.1.20 are affected.",
    "evidence": "cve:CVE-2026-93633",
    "products": [
      {
        "name": {
          "value": "Zimbra Collaboration Suite",
          "evidence": "/containers/cna/affected/0/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-93633",
      "aliases": [
        "CVE-2026-93633"
      ],
      "metrics": [
        {
          "format": "CVSS",
          "cvssV3_1": {
            "scope": "CHANGED",
            "version": "3.1",
            "baseScore": 5.4,
            "attackVector": "NETWORK",
            "baseSeverity": "MEDIUM",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N",
            "integrityImpact": "LOW",
            "userInteraction": "REQUIRED",
            "attackComplexity": "LOW",
            "availabilityImpact": "NONE",
            "privilegesRequired": "LOW",
            "confidentialityImpact": "LOW"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "affected": [
        {
          "vendor": "Zimbra",
          "product": "Zimbra Collaboration Suite",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "versionType": "semver",
              "lessThanOrEqual": "10.1.20"
            }
          ],
          "defaultStatus": "unaffected"
        }
      ],
      "modified": "2026-10-28T19:51:07.972Z",
      "provider": "cve",
      "references": [
        "https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories",
        "https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/"
      ],
      "provider_metadata": {
        "adp": [
          {
            "title": "CISA ADP Vulnrichment",
            "metrics": [
              {
                "other": {
                  "type": "ssvc",
                  "content": {
                    "id": "CVE-2026-93633",
                    "role": "CISA Coordinator",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "version": "2.0.3",
                    "timestamp": "2026-10-28T17:48:57.736632Z"
                  }
                }
              }
            ],
            "providerMetadata": {
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP",
              "dateUpdated": "2026-10-28T19:51:07.972Z"
            }
          }
        ],
        "cna": {
          "orgId": "9974b330-7714-4307-a722-5648477acda7",
          "shortName": "rapid7",
          "dateUpdated": "2026-10-23T13:25:21.365Z"
        }
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-93633",
        "evidence": "/cveMetadata/cveId"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/containers/cna/metrics"
  },
  "source_id": "core-cve",
  "document_id": 482663,
  "published_at": "2026-10-23T13:25:21.365+00:00"
}