All vulnerabilities
CVE-2026-115786

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

Zimbra Zimbra Collaboration SuiteApplications & CMS
Open in ThreatlineRecord JSON
CVSS
6.5Medium
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.44%Chance of exploitation activity in the next 30 days, higher than 36% of CVEs. Scored 24 Oct 2026FIRST EPSS
Fixed inNone listedNo source names a fixed version. Check the vendor advisory below
Published23 Oct 2026Updated 23 Oct 2026CVE List

What fixes it

No source in this snapshot names a fixed version. The vendor advisories under References are the place to check.

Description

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.

Text from CVE List

Affected versions 1

  • Zimbra Collaboration Suiteaffected: all versions through 10.1.20CVE List

References 2