Описание
An attacker that holds a token intended for a different purpose can authenticate, because when an OAuth2 token response does not contain a scope claim, the audience claim is used in its place and checked against the configured required scopes. These are different concepts, and the audience claim does not describe what a token is allowed to do. A token that grants no relevant permissions can be accepted because its intended recipient value happens to match a configured scope name, granting access that should have been denied. It also hides an identity provider misconfiguration where scopes are not being issued at all. Ensure the identity provider issues a scope claim for all tokens used with Dovecot, and that configured scope names do not match audience values. Update to non-vulnerable version. No publicly available exploits are known.
A flaw was found in Dovecot. This vulnerability allows an attacker to bypass authentication by exploiting how OAuth2 tokens are validated. If an OAuth2 token response does not include a scope claim, Dovecot incorrectly uses the audience claim in its place for authorization checks. This can lead to unauthorized access, as a token with no relevant permissions might be accepted if its intended recipient value matches a configured scope name.
Отчет
This vulnerability is rated as Important because an attacker holding a valid token issued for another application can bypass authorization checks and gain unauthorized access to mailboxes. In standard Red Hat Enterprise Linux installations, Dovecot defaults to local system user authentication, leaving OAuth2 disabled unless explicitly configured by an administrator. Consequently, only environments that have explicitly enabled OAuth2 authentication and connect to an Identity Provider that omits token scope claims are susceptible.
Меры по смягчению последствий
To mitigate this issue, ensure that the identity provider issues a scope claim for all tokens used with Dovecot. Additionally, verify that configured scope names in Dovecot do not match audience values from the identity provider. A restart of the Dovecot service may be required for configuration changes to take effect.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 6 | dovecot | Not affected | ||
| Red Hat Enterprise Linux 7 | dovecot | Not 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
7.4 High
CVSS3
Связанные уязвимости
An attacker that holds a token intended for a different purpose can authenticate, because when an OAuth2 token response does not contain a scope claim, the audience claim is used in its place and checked against the configured required scopes. These are different concepts, and the audience claim does not describe what a token is allowed to do. A token that grants no relevant permissions can be accepted because its intended recipient value happens to match a configured scope name, granting access that should have been denied. It also hides an identity provider misconfiguration where scopes are not being issued at all. Ensure the identity provider issues a scope claim for all tokens used with Dovecot, and that configured scope names do not match audience values. Update to non-vulnerable version. No publicly available exploits are known.
An attacker that holds a token intended for a different purpose can authenticate, because when an OAuth2 token response does not contain a scope claim, the audience claim is used in its place and checked against the configured required scopes. These are different concepts, and the audience claim does not describe what a token is allowed to do. A token that grants no relevant permissions can be accepted because its intended recipient value happens to match a configured scope name, granting access that should have been denied. It also hides an identity provider misconfiguration where scopes are not being issued at all. Ensure the identity provider issues a scope claim for all tokens used with Dovecot, and that configured scope names do not match audience values. Update to non-vulnerable version. No publicly available exploits are known.
An attacker that holds a token intended for a different purpose can au ...
An attacker that holds a token intended for a different purpose can authenticate, because when an OAuth2 token response does not contain a scope claim, the audience claim is used in its place and checked against the configured required scopes. These are different concepts, and the audience claim does not describe what a token is allowed to do. A token that grants no relevant permissions can be accepted because its intended recipient value happens to match a configured scope name, granting access that should have been denied. It also hides an identity provider misconfiguration where scopes are not being issued at all. Ensure the identity provider issues a scope claim for all tokens used with Dovecot, and that configured scope names do not match audience values. Update to non-vulnerable version. No publicly available exploits are known.
EPSS
7.4 High
CVSS3