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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-115786
StatePUBLISHED
Assignerrapid7
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-23 14:17:52 UTC
Updated2026-10-23 16:44:17 UTC
DescriptionA 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.

Risk And Classification

Primary CVSS: v3.1 6.5 MEDIUM from [email protected]

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

Problem Types: CWE-682 | CWE-682 CWE-682 Incorrect Calculation

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
3.1CNACVSS6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Zimbra Zimbra Collaboration Suite affected 10.1.20 semver Not specified

References

ReferenceSourceLinkTags
www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1 [email protected] www.rapid7.com
wiki.zimbra.com/wiki/Zimbra_Security_Advisories [email protected] wiki.zimbra.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Jonah Burgess (CryptoCat), Senior Security Researcher, Rapid7 (en)

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