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USN-4993-1: Dovecot vulnerabilities

21 June 2021

Several security issues were fixed in Dovecot.



  • dovecot - IMAP and POP3 email server


Kirin discovered that Dovecot incorrectly escaped kid and azp fields in JWT
tokens. A local attacker could possibly use this issue to validate tokens
using arbitrary keys. This issue only affected Ubuntu 20.10 and Ubuntu
21.04. (CVE-2021-29157)

Fabian Ising and Damian Poddebniak discovered that Dovecot incorrectly
handled STARTTLS when using the SMTP submission service. A remote attacker
could possibly use this issue to inject plaintext commands before
STARTTLS negotiation. (CVE-2021-33515)

Update instructions

The problem can be corrected by updating your system to the following package versions:

Ubuntu 21.04
Ubuntu 20.10
Ubuntu 20.04

In general, a standard system update will make all the necessary changes.