Vulnerability-Lookup

GHSA-H5JF-RFHH-RX8C

Vulnerability from github – Published: 2026-09-25 15:31 – Updated: 2026-09-25 15:31

Details

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.

Severity

9.3 (Critical)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N

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JSON

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{
  "affected": [],
  "aliases": [
    "CVE-2026-93647"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-25T14:17:23Z",
    "severity": "CRITICAL"
  },
  "details": "An unauthenticated calendar sender can place active markup in a COUNTER message\u0027s RFC\u00a0From\u00a0address. Selecting the message in Zimbra Classic triggers stored XSS, allowing the attacker to access mailbox data and act as the victim.",
  "id": "GHSA-h5jf-rfhh-rx8c",
  "modified": "2026-09-25T15:31:48Z",
  "published": "2026-09-25T15:31:48Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-93647"
    },
    {
      "type": "WEB",
      "url": "https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-93647 (GCVE-0-2026-93647)

Vulnerability from cvelistv5 – Published: 2026-09-25 13:58 – Updated: 2026-09-25 13:58

Title

Zimbra Collaboration Suite Classic Web Client Stored Cross-Site Scripting via Crafted Calendar COUNTER Message From Address

Summary

Severity

9.3 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N

CWE

CWE-79 - Improper neutralization of input during web page generation ('cross-site scripting')

Assigner

rapid7 mitre root

References

1 reference

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

Impacted products

1 product

Vendor	Product	Version
Zimbra	Zimbra Collaboration Suite (ZCS)	Affected: 0 , < 10.1.21 (semver)

Date Public

2026-09-25 13:53

Credits

Jonah Burgess (CryptoCat), Senior Security Researcher, Rapid7

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JSON

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{
  "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\u0027s RFC\u0026nbsp;\u003ccode\u003eFrom\u003c/code\u003e\u0026nbsp;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\u0027s 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 (\u0027cross-site scripting\u0027)",
              "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"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

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GHSA-H5JF-RFHH-RX8C

CVE-2026-93647 (GCVE-0-2026-93647)

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