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                                  CERT-Renater

                      Note d'Information No. 2022/VULN238

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DATE                : 07/07/2022

HARDWARE PLATFORM(S): /

OPERATING SYSTEM(S): Systems running Dovecot IMAP Server.

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https://dovecot.org/pipermail/dovecot-news/2022-July/000477.html
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Affected product: Dovecot IMAP Server
Internal reference: DOV-5320
Vulnerability type: Improper Access Control (CWE-284)
Vulnerable version: 2.2
Vulnerable component: submission
Report confidence: Confirmed
Solution status: Fixed in main
Researcher credits: Julian Brook (julezman)
Vendor notification: 2022-05-06
CVE reference: CVE-2022-30550
CVSS: 6.8 (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N)


Vulnerability Details:

When two passdb configuration entries exist in Dovecot configuration,
which have the same driver and args settings, the incorrect
username_filter and mechanism settings can be applied to passdb
definitions. These incorrectly applied settings can lead to an
unintended security configuration and can permit privilege
escalation with certain configurations involving master user
authentication.

Dovecot documentation does not advise against the use of passdb
definitions which have the same driver and args settings. One
such configuration would be where an administrator wishes to
use the same pam configuration or passwd file for both normal
and master users but use the username_filter setting to
restrict which of the users is able to be a master user.


Risk:
If same passwd file or PAM is used for both normal and master
users, it is possible for attacker to become master user.

Workaround:
Always authenticate master users from different source than
regular users, e.g. using a separate passwd file. Alternatively,
you can use global ACLs to ensure that only legimate master users
have priviledged access.


Fix:
This has been fixed in main branch.
See https://github.com/dovecot/core/compare/7bad6a24%5E..a1022072.patch


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+ CERT-RENATER        |    tel : 01-53-94-20-44         +
+ 23/25 Rue Daviel    |    fax : 01-53-94-20-41         +
+ 75013 Paris         |   email:cert@support.renater.fr +
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