{"cve":"CVE-2026-40017","nvd":{"published":"2026-08-28T12:16:28.480","modified":"2026-09-03T18:13:44.643","status":"Deferred","description":"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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H","score":6.5},"cwes":["CWE-400"],"references":["https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0003.json"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:50:50.842544443+00:00"},"epss":{"cve":"CVE-2026-40017","score":0.00334,"percentile":0.26821,"date":"2026-11-01"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}