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    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2026-93628",
        "assignerOrgId": "9974b330-7714-4307-a722-5648477acda7",
        "state": "PUBLISHED",
        "assignerShortName": "rapid7",
        "dateReserved": "2026-09-18T12:22:34.911Z",
        "datePublished": "2026-10-23T13:18:16.368Z",
        "dateUpdated": "2026-10-23T13:18:16.368Z"
    },
    "containers": {
        "cna": {
            "providerMetadata": {
                "orgId": "9974b330-7714-4307-a722-5648477acda7",
                "shortName": "rapid7",
                "dateUpdated": "2026-10-23T13:18:16.368Z"
            },
            "title": "Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar REPLY Attendee Response",
            "datePublic": "2026-10-23T12:46:00.000Z",
            "problemTypes": [
                {
                    "descriptions": [
                        {
                            "lang": "en",
                            "cweId": "CWE-290",
                            "description": "CWE-290 Authentication bypass by spoofing",
                            "type": "CWE"
                        }
                    ]
                }
            ],
            "affected": [
                {
                    "vendor": "Zimbra",
                    "product": "Zimbra Collaboration Suite",
                    "versions": [
                        {
                            "status": "affected",
                            "version": "0",
                            "lessThanOrEqual": "10.1.21",
                            "versionType": "semver"
                        }
                    ],
                    "defaultStatus": "unaffected"
                }
            ],
            "descriptions": [
                {
                    "lang": "en",
                    "value": "An attendee authentication vulnerability in the email calendar processing of Zimbra Collaboration Suite (ZCS) allows an unauthenticated sender to forge another attendee's response to an existing meeting. Zimbra passes a null sender identity when processing iCalendar REPLY components, causing the attendee authorization filter to be skipped. An attacker who knows the meeting UID, organizer address and attendee address can send a non-outdated reply that changes the attendee's participation status in the organizer's calendar. The change occurs automatically during delivery without organizer or attendee interaction. ZCS 10.1.16 and 10.1.21 are affected.",
                    "supportingMedia": [
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                            "value": "An attendee authentication vulnerability in the email calendar processing of Zimbra Collaboration Suite (ZCS) allows an unauthenticated sender to forge another attendee's response to an existing meeting. Zimbra passes a null sender identity when processing iCalendar REPLY components, causing the attendee authorization filter to be skipped. An attacker who knows the meeting UID, organizer address and attendee address can send a non-outdated reply that changes the attendee's participation status in the organizer's calendar. The change occurs automatically during delivery without organizer or attendee interaction. ZCS 10.1.16 and 10.1.21 are affected."
                        }
                    ]
                }
            ],
            "references": [
                {
                    "url": "https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories",
                    "tags": [
                        "vendor-advisory"
                    ]
                },
                {
                    "url": "https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/",
                    "tags": [
                        "related"
                    ]
                }
            ],
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                    "format": "CVSS",
                    "scenarios": [
                        {
                            "lang": "en",
                            "value": "GENERAL"
                        }
                    ],
                    "cvssV3_1": {
                        "version": "3.1",
                        "attackVector": "NETWORK",
                        "attackComplexity": "LOW",
                        "privilegesRequired": "NONE",
                        "userInteraction": "NONE",
                        "scope": "UNCHANGED",
                        "confidentialityImpact": "NONE",
                        "integrityImpact": "LOW",
                        "availabilityImpact": "NONE",
                        "baseSeverity": "MEDIUM",
                        "baseScore": 5.3,
                        "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"
                    }
                }
            ],
            "credits": [
                {
                    "lang": "en",
                    "value": "Jonah Burgess (CryptoCat), Senior Security Researcher, Rapid7",
                    "type": "finder"
                }
            ],
            "source": {
                "discovery": "UNKNOWN"
            },
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}