Vulnerability-Lookup

GHSA-W5XC-29C5-3J2H

Vulnerability from github – Published: 2026-10-23 15:31 – Updated: 2026-10-23 15:31

Details

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.

Severity

6.5 (Medium)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-115786"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-682"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-23T14:17:52Z",
    "severity": "MODERATE"
  },
  "details": "A mailbox quota-accounting vulnerability in Zimbra Collaboration Suite (ZCS) allows an authenticated user to consume another user\u2019s mailbox quota by repeatedly sharing and revoking a document. Creation of the recipient\u2019s 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.",
  "id": "GHSA-w5xc-29c5-3j2h",
  "modified": "2026-10-23T15:31:38Z",
  "published": "2026-10-23T15:31:38Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-115786"
    },
    {
      "type": "WEB",
      "url": "https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories"
    },
    {
      "type": "WEB",
      "url": "https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-115786 (GCVE-0-2026-115786)

Vulnerability from cvelistv5 – Published: 2026-10-23 13:53 – Updated: 2026-10-23 13:53

Title

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

Summary

Severity

6.5 (Medium)


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

CWE

CWE-682 - Incorrect Calculation

Assigner

rapid7 CNA under the mitre root

CNA scorecard B 76/100 over 81 records in the last 180 days details

References

2 references

URL	Tags
https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories	vendor-advisory
https://www.rapid7.com/blog/post/ve-breaking-zimb…	related

Impacted products

1 product

Vendor	Product	Version
Zimbra	Zimbra Collaboration Suite	Affected: 0 , ≤ 10.1.20 (semver)

Date Public

2026-10-23 13:51

Credits

Jonah Burgess (CryptoCat), Senior Security Researcher, Rapid7

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JSON

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Zimbra Collaboration Suite",
          "vendor": "Zimbra",
          "versions": [
            {
              "lessThanOrEqual": "10.1.20",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Jonah Burgess (CryptoCat), Senior Security Researcher, Rapid7"
        }
      ],
      "datePublic": "2026-10-23T13:51:00.000Z",
      "descriptions": [
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              "type": "text/html",
              "value": "A mailbox quota-accounting vulnerability in Zimbra Collaboration Suite (ZCS) allows an authenticated user to consume another user\u2019s mailbox quota by repeatedly sharing and revoking a document. Creation of the recipient\u2019s 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."
            }
          ],
          "value": "A mailbox quota-accounting vulnerability in Zimbra Collaboration Suite (ZCS) allows an authenticated user to consume another user\u2019s mailbox quota by repeatedly sharing and revoking a document. Creation of the recipient\u2019s 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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
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        "orgId": "9974b330-7714-4307-a722-5648477acda7",
        "shortName": "rapid7"
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      "references": [
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          "tags": [
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          ],
          "url": "https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories"
        },
        {
          "tags": [
            "related"
          ],
          "url": "https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/"
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "Zimbra Collaboration Suite Shared-File Mailbox Quota Accounting Error Enables Quota Exhaustion",
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    "datePublished": "2026-10-23T13:53:33.918Z",
    "dateReserved": "2026-10-23T13:41:21.016Z",
    "dateUpdated": "2026-10-23T13:53:33.918Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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