Описание
When mail_max_userip_connections is set (default 10) and reached, submission-login can crash with epoll() panic caused by file descriptor handling issues. If running in high-security mode (default for community releases), only the new submission connection gets terminated. If running in high-performance mode (default for Pro releases), all connections handled by the submission-login process will be terminated. The crashes can cause failure for user to send a message, or it can cause duplicate messages to be sent. If TLS is not used (in the backend server processing the submission), duplicate deliveries cannot happen, because the crash can only happen at AUTH stage. Limit the number of connections handled by single submission-login process. This has a performance impact though. Update to non-vulnerable version. No publicly available exploits are known.
A flaw was found in the Dovecot mail server's submission-login component. This vulnerability occurs when the server reaches its maximum allowed user IP connections, leading to a crash due to file descriptor handling issues. This can result in a denial of service, preventing users from sending emails, and potentially causing duplicate message delivery under certain conditions.
Отчет
Red Hat has evaluated this vulnerability as having an Important severity rating because an authenticated user can crash the mail submission service and trigger duplicate message deliveries, compromising both service availability and message integrity. While exploitation requires network access to the submission interface and valid authentication credentials, the resulting process termination causes delivery failures and risk of unintended retransmissions. On Red Hat Enterprise Linux systems, Dovecot enforces per-IP connection limits by default, exposing submission login services to crashes when connection thresholds are exhausted.
Меры по смягчению последствий
To mitigate this issue, limit the number of connections handled by a single submission-login process. This can be achieved by adjusting the process_limit setting for the submission-login service in the Dovecot configuration. For example, add or modify the following in a Dovecot configuration file (e.g., /etc/dovecot/conf.d/10-master.conf):
Reducing this limit may impact performance. After modifying the configuration, restart the Dovecot service for the changes to take effect.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 6 | dovecot | Out of support scope | ||
| Red Hat Enterprise Linux 7 | dovecot | Affected | ||
| Red Hat Enterprise Linux 10 | dovecot | Fixed | RHSA-2026:79371 | 08.10.2026 |
| Red Hat Enterprise Linux 8 | dovecot | Fixed | RHSA-2026:76763 | 06.10.2026 |
| Red Hat Enterprise Linux 9 | dovecot | Fixed | RHSA-2026:80825 | 12.10.2026 |
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Дополнительная информация
Статус:
EPSS
7.1 High
CVSS3
Связанные уязвимости
When mail_max_userip_connections is set (default 10) and reached, submission-login can crash with epoll() panic caused by file descriptor handling issues. If running in high-security mode (default for community releases), only the new submission connection gets terminated. If running in high-performance mode (default for Pro releases), all connections handled by the submission-login process will be terminated. The crashes can cause failure for user to send a message, or it can cause duplicate messages to be sent. If TLS is not used (in the backend server processing the submission), duplicate deliveries cannot happen, because the crash can only happen at AUTH stage. Limit the number of connections handled by single submission-login process. This has a performance impact though. Update to non-vulnerable version. No publicly available exploits are known.
When mail_max_userip_connections is set (default 10) and reached, submission-login can crash with epoll() panic caused by file descriptor handling issues. If running in high-security mode (default for community releases), only the new submission connection gets terminated. If running in high-performance mode (default for Pro releases), all connections handled by the submission-login process will be terminated. The crashes can cause failure for user to send a message, or it can cause duplicate messages to be sent. If TLS is not used (in the backend server processing the submission), duplicate deliveries cannot happen, because the crash can only happen at AUTH stage. Limit the number of connections handled by single submission-login process. This has a performance impact though. Update to non-vulnerable version. No publicly available exploits are known.
When mail_max_userip_connections is set (default 10) and reached, subm ...
EPSS
7.1 High
CVSS3