{"id":"CVE-2026-115786","title":"Zimbra Collaboration Suite Shared-File Mailbox Quota Accounting Error Enables Quota Exhaustion","summary":"A mailbox quota-accounting vulnerability in Zimbra Collaboration Suite (ZCS) allows an authenticated user to consume another user’s mailbox quota by repeatedly sharing and revoking a document. Creation of the recipient’s shared-file reco…","severity":"medium","cvss":6.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","cvssSource":"cna","cwe":["CWE-682"],"vendor":"Zimbra","product":"Zimbra Collaboration Suite","affected":["collaboration_suite <= 10.1.20"],"published":"2026-10-23","updated":"2026-10-23","sourceUpdated":"2026-10-23T13:53:33.918Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-115786","references":[{"url":"https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories"},{"url":"https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/"}],"tags":["cve.org"],"ingestedAt":"2026-10-23T14:28:08.698Z","slug":"CVE-2026-115786","body":"## Overview\n\nA mailbox quota-accounting vulnerability in Zimbra Collaboration Suite (ZCS) allows an authenticated user to consume another user’s mailbox quota by repeatedly sharing and revoking a document. Creation of the recipient’s shared-file record charges the document size to mailbox-wide usage. Revocation deletes the record and reverses its folder counters without reversing the mailbox-wide charge. Repeated normal share notifications therefore accumulate quota usage after the visible records are gone. On accounts with a finite quota, this can prevent incoming mail and other size-increasing operations without recipient interaction. The issue affects ZCS 10.1.16 and 10.1.20.\n\n## Affected\n\n- `collaboration_suite <= 10.1.20`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":36,"depthScoreParts":{"impact":35.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}