CVE-2026-93647

Description

An unauthenticated calendar sender can place active markup in a COUNTER message's RFC From address. Selecting the message in Zimbra Classic triggers stored XSS, allowing the attacker to access mailbox data and act as the victim.

Overview

State: PUBLISHED
Assigner (CNA): rapid7
CVSS severity: CRITICAL
CVSS score: 9.3 / 10
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
Effective score: 9.3 / 10 CRITICAL source: CNA overview
CWE(s): CWE-79
Reserved: 2026-09-18
Published: 2026-09-25 13:58 UTC
Last updated: 2026-09-25 13:58 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/93xxx/CVE-2026-93647.json
Linked Threat: CVE-2026-93647 — Zimbra Collaboration Suite Classic Web Client Stored Cross-Site Scripting via Crafted Calendar COUNTER Message From Address

NVD triage scoring NVD CVE 2.0

Layer NVD adds on top of the CNA's CVE record — published / last-modified timestamps, exploitability / impact subscores, and the FIRST.org EPSS probability that this CVE will be exploited in the wild in the next 30 days.

NVD published: 2026-09-25 14:17:23 UTC
NVD last modified: 2026-09-26 04:17:52 UTC
NVD CVSS v3.1: 9.3 / 10 CRITICAL source: cve@rapid7.com
NVD CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
Exploitability subscore: 2.8 / 10
Impact subscore: 5.8 / 10

Affected products (1)

Vendor	Product	Versions	Platforms
Zimbra	Zimbra Collaboration Suite (ZCS)	`0` (affected)	—

Vendor references (1)

References embedded in the original CVE record by the assigning CNA.

https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories vendor-advisory

Web references (0)

DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.

No web references attached yet.

NVD-tagged references (1)

Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.

https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories cve@rapid7.com

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-93647.json.

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Zimbra Collaboration Suite (ZCS)",
          "vendor": "Zimbra",
          "versions": [
            {
              "lessThan": "10.1.21",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Jonah Burgess (CryptoCat), Senior Security Researcher, Rapid7"
        }
      ],
      "datePublic": "2026-09-25T13:53:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "An unauthenticated calendar sender can place active markup in a COUNTER message's RFC&nbsp;<code>From</code>&nbsp;address. Selecting the message in Zimbra Classic triggers stored XSS, allowing the attacker to access mailbox data and act as the victim."
            }
          ],
          "value": "An unauthenticated calendar sender can place active markup in a COUNTER message's RFC\u00a0From\u00a0address. Selecting the message in Zimbra Classic triggers stored XSS, allowing the attacker to access mailbox data and act as the victim."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 9.3,
            "baseSeverity": "CRITICAL",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "CHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-79",
              "description": "CWE-79 Improper neutralization of input during web page generation ('cross-site scripting')",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-25T13:58:05.368Z",
        "orgId": "9974b330-7714-4307-a722-5648477acda7",
        "shortName": "rapid7"
      },
      "references": [
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories"
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "Zimbra Collaboration Suite Classic Web Client Stored Cross-Site Scripting via Crafted Calendar COUNTER Message From Address",
      "x_generator": {
        "engine": "Vulnogram 1.0.5"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "9974b330-7714-4307-a722-5648477acda7",
    "assignerShortName": "rapid7",
    "cveId": "CVE-2026-93647",
    "datePublished": "2026-09-25T13:58:05.368Z",
    "dateReserved": "2026-09-18T12:22:43.194Z",
    "dateUpdated": "2026-09-25T13:58:05.368Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}