CVE-2020-7046: Truncated UTF-8 can be used to DoS submission-login and lmtp processes

[Aki Tuomi]

Open-Xchange Security Advisory 2020-02-12

Affected product: Dovecot Core
Internal reference: DOV-3744 (JIRA ID)
Vulnerability type: Improper Input Validation (CWE-30)
Vulnerable version: 2.3.9
Vulnerable component: submission-login, lmtp
Fixed version: 2.3.9.3
Report confidence: Confirmed
Solution status: Fixed
Researcher credits: Open-Xchange oy
Vendor notification: 2020-01-14
CVE reference: CVE-2020-7046
CVSS: 7.5 (CVSS3.1:AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

Vulnerability Details:

lib-smtp doesn't handle truncated command parameters properly, resulting
in infinite loop taking 100% CPU for the process. This happens for LMTP
(where it doesn't matter so much) and also for submission-login where
unauthenticated users can trigger it.

Risk:

Attacker can cause submission-login and lmtp processes to be exhausted,
leading into denial of service and CPU resource exhaustion.

Solution:

Upgrade to 2.3.9.3.


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