SEPTEMBER 17, 2026
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Case File

CVE-2026-40017

MEDIUM · CVSS 6.5 EPSS 0.27% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-08-28 · Last synced 2026-09-17

CyberRota Analysis

AI-Generated

The vulnerability allows an attacker to craft a malicious email header that can cause excessive CPU consumption when the IMAP THREAD command is executed on the affected mailbox, potentially leading to service degradation or denial of service. Organizations using email systems that support IMAP should prioritize this issue, particularly those with high email traffic, to prevent potential disruptions. Monitoring for abnormal CPU usage and updating to a non-vulnerable version are recommended mitigation strategies.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Detected Signals
exploit

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-40017
Severity
MEDIUM
CVSS
6.5
EPSS
0.27%

Original NVD 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.