Vulnerabilities / CVE-2026-115786

CVE-2026-115786

Published 2026-10-23 · published (not yet in NVD)

CVE-2026-115786

Zimbra Collaboration Suite Shared-File Mailbox Quota Accounting Error Enables Quota Exhaustion

6.5 MEDIUM
CVSS 3.1 · CNA

0.4%
chance of exploitation in the next 30 days (EPSS; higher than 31% of CVEs)

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 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.

Scores

6.5CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HCNA

Affected products

Zimbra Zimbra Collaboration Suite: 0 to ≤ 10.1.20

Weakness: CWE-682

2 references (advisories, patches, write-ups)

https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories · vendor-advisory
https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/ · related

Sources: CVE.org, FIRST EPSS. Missing ones did not answer or have no record yet.

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