Bug 1673415 (CVE-2019-3814) - CVE-2019-3814 dovecot: Improper certificate validation
Summary: CVE-2019-3814 dovecot: Improper certificate validation
Status: NEW
Alias: CVE-2019-3814
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard: impact=moderate,public=20190205,repor...
Keywords: Security
Depends On: 1674369 1674370 1673416
Blocks: 1673418
TreeView+ depends on / blocked
 
Reported: 2019-02-07 13:23 UTC by Dhananjay Arunesh
Modified: 2019-06-08 23:51 UTC (History)
1 user (show)

(edit)
It was discovered that Dovecot incorrectly handled client certificates. A remote attacker in possession of a valid certificate with an empty username field could possibly use this issue to impersonate other users.
Clone Of:
(edit)
Last Closed:


Attachments (Terms of Use)

Description Dhananjay Arunesh 2019-02-07 13:23:30 UTC
It was discovered that Dovecot incorrectly handled client certificates. A
remote attacker in possession of a valid certificate with an empty username
field could possibly use this issue to impersonate other users.

References:
https://security-tracker.debian.org/tracker/source-package/dovecot
https://usn.ubuntu.com/usn/usn-3881-1
https://usn.ubuntu.com/usn/usn-3881-2

Comment 1 Dhananjay Arunesh 2019-02-07 13:23:50 UTC
Created dovecot tracking bugs for this issue:

Affects: fedora-all [bug 1673416]

Comment 2 Dhananjay Arunesh 2019-02-07 14:22:53 UTC
External References:

https://www.dovecot.org/list/dovecot/2019-February/114575.html

Comment 3 Huzaifa S. Sidhpurwala 2019-02-11 07:16:27 UTC
This basically affects installation which enable client-side certs. When authenticating with a cert which has empty "user" field, vulnerable versions take the loginame from the user. If no additional password is configured this will allow the user to impersonate anyone else in the system.

Comment 4 Huzaifa S. Sidhpurwala 2019-02-11 07:16:30 UTC
Mitigation:

Attack can be migitated by having the certificates with proper Extended Key Usage, such as 'TLS Web Server' and 'TLS Web Server Client'. Also client-side certification authentication can be turned off using:
auth_ssl_require_client_cert = no
auth_ssl_username_from_cert = no


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