Описание
An unauthenticated attacker can crash the ManageSieve login process by sending a small malformed command before authenticating. If running in high-security mode (default for community releases), only the attacker's own connection is terminated. If running in high-performance mode (default for Pro releases), all connections handled by the same managesieve-login process are terminated. Repeating the attack can cause denial of service for Sieve script management. Restrict network access to the ManageSieve service to trusted clients. Update to non-vulnerable version. No publicly available exploits are known.
A flaw was found in Dovecot. An unauthenticated attacker can crash the ManageSieve login process by sending a small malformed command before authenticating. This can lead to a denial of service for Sieve script management, affecting either the attacker's connection or all connections handled by the same process, depending on the security mode.
Отчет
This vulnerability is rated as Important because an unauthenticated remote attacker can crash the ManageSieve login daemon, causing a denial of service for mail filtering administration without requiring valid credentials. In standard Red Hat Enterprise Linux environments, the ManageSieve protocol is not enabled by default and runs isolated from primary IMAP and POP3 delivery processes. Consequently, systems that do not explicitly configure the Sieve protocol listener are not affected, and core mailbox operations remain fully functional even during an attack.
Меры по смягчению последствий
Restrict network access to the ManageSieve service to trusted clients only. This can be achieved by configuring a firewall to limit incoming connections to the service's port (e.g., 4190 for Sieve) from specific IP addresses or networks. For example, using firewalld:
Replace <TRUSTED_IP_OR_NETWORK> with the actual trusted source. A firewall reload is required for 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:
7.5 High
CVSS3
Связанные уязвимости
An unauthenticated attacker can crash the ManageSieve login process by sending a small malformed command before authenticating. If running in high-security mode (default for community releases), only the attacker's own connection is terminated. If running in high-performance mode (default for Pro releases), all connections handled by the same managesieve-login process are terminated. Repeating the attack can cause denial of service for Sieve script management. Restrict network access to the ManageSieve service to trusted clients. Update to non-vulnerable version. No publicly available exploits are known.
An unauthenticated attacker can crash the ManageSieve login process by sending a small malformed command before authenticating. If running in high-security mode (default for community releases), only the attacker's own connection is terminated. If running in high-performance mode (default for Pro releases), all connections handled by the same managesieve-login process are terminated. Repeating the attack can cause denial of service for Sieve script management. Restrict network access to the ManageSieve service to trusted clients. Update to non-vulnerable version. No publicly available exploits are known.
An unauthenticated attacker can crash the ManageSieve login process by ...
An unauthenticated attacker can crash the ManageSieve login process by sending a small malformed command before authenticating. If running in high-security mode (default for community releases), only the attacker's own connection is terminated. If running in high-performance mode (default for Pro releases), all connections handled by the same managesieve-login process are terminated. Repeating the attack can cause denial of service for Sieve script management. Restrict network access to the ManageSieve service to trusted clients. Update to non-vulnerable version. No publicly available exploits are known.
7.5 High
CVSS3