dovecot - Jul 2022 - CVE-2022-30550: Privilege escalation possible in dovecot when similar master and non-master passdbs are used

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

> On 06/07/2022 16:54 EEST Aki Tuomi via Dovecot-news <dovecot-news at
dovecot.org> wrote:
> 
>  
> 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
Two small corrections to this CVE notice... The service impacted is of course
'auth' not 'submission', and the version impacted is from 2.2 to
2.3.19.1.

Aki