Vulnerability-Lookup

GHSA-77GQ-8M6P-2C3G

Vulnerability from github – Published: 2026-10-23 15:31 – Updated: 2026-10-23 15:31

Details

An organizer authentication vulnerability in the email calendar processing of Zimbra Collaboration Suite (ZCS) allows an unauthenticated sender to cancel or modify an existing meeting in a recipient's calendar. Zimbra accepts iCalendar CANCEL and REQUEST components without verifying that the email sender is authorized to act as the supplied organizer. An attacker who knows the meeting UID and organizer address can supply a non-outdated sequence number to move the recipient's meeting to Trash or replace its details. Processing occurs automatically during email delivery without recipient interaction. ZCS 10.1.16 and 10.1.21 are affected.

Severity

5.3 (Medium)


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

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-93627"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-290"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-23T14:17:56Z",
    "severity": "MODERATE"
  },
  "details": "An organizer authentication vulnerability in the email calendar processing of Zimbra Collaboration Suite (ZCS) allows an unauthenticated sender to cancel or modify an existing meeting in a recipient\u0027s calendar. Zimbra accepts iCalendar CANCEL and REQUEST components without verifying that the email sender is authorized to act as the supplied organizer. An attacker who knows the meeting UID and organizer address can supply a non-outdated sequence number to move the recipient\u0027s meeting to Trash or replace its details. Processing occurs automatically during email delivery without recipient interaction. ZCS 10.1.16 and 10.1.21 are affected.",
  "id": "GHSA-77gq-8m6p-2c3g",
  "modified": "2026-10-23T15:31:38Z",
  "published": "2026-10-23T15:31:38Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-93627"
    },
    {
      "type": "WEB",
      "url": "https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories"
    },
    {
      "type": "WEB",
      "url": "https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-93627 (GCVE-0-2026-93627)

Vulnerability from cvelistv5 – Published: 2026-10-23 13:17 – Updated: 2026-10-23 13:17

Title

Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar CANCEL/REQUEST Organizer

Summary

Severity

5.3 (Medium)


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

CWE

CWE-290 - Authentication bypass by spoofing

Assigner

rapid7 CNA under the mitre root

CNA scorecard B 76/100 over 81 records in the last 180 days details

References

2 references

URL	Tags
https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories	vendor-advisory
https://www.rapid7.com/blog/post/ve-breaking-zimb…	related

Impacted products

1 product

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

Date Public

2026-10-23 12:44

Credits

Jonah Burgess (CryptoCat), Senior Security Researcher, Rapid7

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Zimbra Collaboration Suite",
          "vendor": "Zimbra",
          "versions": [
            {
              "lessThanOrEqual": "10.1.21",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Jonah Burgess (CryptoCat), Senior Security Researcher, Rapid7"
        }
      ],
      "datePublic": "2026-10-23T12:44:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "An organizer authentication vulnerability in the email calendar processing of Zimbra Collaboration Suite (ZCS) allows an unauthenticated sender to cancel or modify an existing meeting in a recipient\u0027s calendar. Zimbra accepts iCalendar CANCEL and REQUEST components without verifying that the email sender is authorized to act as the supplied organizer. An attacker who knows the meeting UID and organizer address can supply a non-outdated sequence number to move the recipient\u0027s meeting to Trash or replace its details. Processing occurs automatically during email delivery without recipient interaction. ZCS 10.1.16 and 10.1.21 are affected."
            }
          ],
          "value": "An organizer authentication vulnerability in the email calendar processing of Zimbra Collaboration Suite (ZCS) allows an unauthenticated sender to cancel or modify an existing meeting in a recipient\u0027s calendar. Zimbra accepts iCalendar CANCEL and REQUEST components without verifying that the email sender is authorized to act as the supplied organizer. An attacker who knows the meeting UID and organizer address can supply a non-outdated sequence number to move the recipient\u0027s meeting to Trash or replace its details. Processing occurs automatically during email delivery without recipient interaction. ZCS 10.1.16 and 10.1.21 are affected."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-290",
              "description": "CWE-290 Authentication bypass by spoofing",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-23T13:17:00.739Z",
        "orgId": "9974b330-7714-4307-a722-5648477acda7",
        "shortName": "rapid7"
      },
      "references": [
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories"
        },
        {
          "tags": [
            "related"
          ],
          "url": "https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/"
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar CANCEL/REQUEST Organizer",
      "x_generator": {
        "engine": "Vulnogram 1.0.5"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "9974b330-7714-4307-a722-5648477acda7",
    "assignerShortName": "rapid7",
    "cveId": "CVE-2026-93627",
    "datePublished": "2026-10-23T13:17:00.739Z",
    "dateReserved": "2026-09-18T12:22:34.911Z",
    "dateUpdated": "2026-10-23T13:17:00.739Z",
    "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.

Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

Order JSON

Publication & reservation Sightings KEV catalogs Other timestamps

Loading timeline…

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.

Related by attack behaviour

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.

Action not permitted