CVE-2026-42006

A flaw was found in Dovecot. A remote attacker can exploit this vulnerability by sending excessive open braces over the Internet Message Access Protocol (IMAP), leading to uncontrolled memory usage. This can cause the affected system to consume memory up to its configured limit, resulting in a Denial of Service (DoS).

A remote attacker can trigger this flaw simply by sending specially crafted IMAP requests to the Dovecot server, requiring no complex interactions.

The vulnerability is strictly limited to a Denial of Service (DoS) via memory exhaustion and does not allow for data exfiltration, privilege escalation, or remote code execution. Furthermore, the impact is contained because the memory consumption is restricted to the process's configured limit, preventing a complete system-wide crash.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, administrators can configure the vsz_limit setting for the Dovecot IMAP process to a lower value. This limits the virtual memory size available to the IMAP process, preventing excessive memory consumption.

Example configuration in /etc/dovecot/conf.d/10-master.conf:

service imap {
  vsz_limit = 256M
}

After modifying the configuration, restart the Dovecot service for the changes to take effect.

systemctl restart dovecot

Setting vsz_limit too low may impact legitimate IMAP operations.

*Restarting the dovecot service will temporarily interrupt mail services.