Vulnerability-Lookup

GHSA-GR5F-599W-CG8J

Vulnerability from github – Published: 2026-08-28 12:30 – Updated: 2026-08-28 12:30

Details

An attacker that can send mail to a user can craft a message header whose values are chosen to collide in an internal hash table, which makes the IMAP THREAD command consume CPU disproportionate to the size of the message. This is a separate issue from CVE-2026-40014 and is not addressed by that fix. Whenever a mail client issues a THREAD command on the affected mailbox, this can cause degradation or denial of service for IMAP. Monitor system for abnormal CPU usage, kill the offending process and remove the offending message from the affected mailbox. Update to non-vulnerable version. No publicly available exploits are known.

Severity

6.5 (Medium)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-40017"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-28T12:16:28Z",
    "severity": "MODERATE"
  },
  "details": "An attacker that can send mail to a user can craft a message header whose values are chosen to collide in an internal hash table, which makes the IMAP THREAD command consume CPU disproportionate to the size of the message. This is a separate issue from CVE-2026-40014 and is not addressed by that fix. Whenever a mail client issues a THREAD command on the affected mailbox, this can cause degradation or denial of service for IMAP. Monitor system for abnormal CPU usage, kill the offending process and remove the offending message from the affected mailbox. Update to non-vulnerable version. No publicly available exploits are known.",
  "id": "GHSA-gr5f-599w-cg8j",
  "modified": "2026-08-28T12:30:25Z",
  "published": "2026-08-28T12:30:25Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-40017"
    },
    {
      "type": "WEB",
      "url": "https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0003.json"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-40017 (GCVE-0-2026-40017)

Vulnerability from cvelistv5 – Published: 2026-08-28 10:12 – Updated: 2026-08-28 15:02

Summary

Severity

6.5 (Medium)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-28 15:00 UTC

CWE

CWE-400 - Uncontrolled Resource Consumption

Assigner

OX mitre root

References

1 reference

URL	Tags
https://documentation.open-xchange.com/dovecot/se…	vendor-advisory

Impacted products

2 products

Vendor	Product	Version
Open-Xchange GmbH	OX Dovecot Pro	Affected: 2.3.0 , < 2.3.22.2 (semver) Affected: 3.0.0 , < 3.0.7 (semver) Affected: 3.1.0 , < 3.1.6 (semver)
Open-Xchange GmbH	OX Dovecot CE	Affected: 2.3.0 , < 2.4.5 (semver)

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-40017",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-28T15:00:50.670534Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-28T15:02:36.570Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "modules": [
            "core"
          ],
          "product": "OX Dovecot Pro",
          "vendor": "Open-Xchange GmbH",
          "versions": [
            {
              "lessThan": "2.3.22.2",
              "status": "affected",
              "version": "2.3.0",
              "versionType": "semver"
            },
            {
              "lessThan": "3.0.7",
              "status": "affected",
              "version": "3.0.0",
              "versionType": "semver"
            },
            {
              "lessThan": "3.1.6",
              "status": "affected",
              "version": "3.1.0",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "unaffected",
          "modules": [
            "core"
          ],
          "product": "OX Dovecot CE",
          "vendor": "Open-Xchange GmbH",
          "versions": [
            {
              "lessThan": "2.4.5",
              "status": "affected",
              "version": "2.3.0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "An attacker that can send mail to a user can craft a message header whose values are chosen to collide in an internal hash table, which makes the IMAP THREAD command consume CPU disproportionate to the size of the message. This is a separate issue from CVE-2026-40014 and is not addressed by that fix. Whenever a mail client issues a THREAD command on the affected mailbox, this can cause degradation or denial of service for IMAP. Monitor system for abnormal CPU usage, kill the offending process and remove the offending message from the affected mailbox. Update to non-vulnerable version. No publicly available exploits are known."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-400",
              "description": "Uncontrolled Resource Consumption",
              "lang": "en",
              "type": "cwe"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-28T10:30:43.636Z",
        "orgId": "8ce71d90-2354-404b-a86e-bec2cc4e6981",
        "shortName": "OX"
      },
      "references": [
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0003.json"
        }
      ],
      "source": {
        "defect": "DOV-9047",
        "discovery": "EXTERNAL"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "8ce71d90-2354-404b-a86e-bec2cc4e6981",
    "assignerShortName": "OX",
    "cveId": "CVE-2026-40017",
    "datePublished": "2026-08-28T10:12:19.524Z",
    "dateReserved": "2026-04-08T09:59:59.342Z",
    "dateUpdated": "2026-08-28T15:02:36.570Z",
    "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.

Detection rules are retrieved from Rulezet.

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.

Action not permitted

GHSA-GR5F-599W-CG8J

CVE-2026-40017 (GCVE-0-2026-40017)

Tags

Sightings

Nomenclature