Remote code execution in Dovecot IMAP server

1) Out-of-bounds write

EUVDB-ID: #VU20432

Risk: High

CVSSv3.1: 8.8 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2019-11500

CWE-ID: CWE-787 - Out-of-bounds write

Exploit availability: No

Description

The vulnerability allows a remote attacker to compromise vulnerable system.

The vulnerability exists due to a boundary error within IMAP and ManageSieve protocol implementation the when scanning data in quoted strings. A remote attacker can send a specially crafted request to the affected server, trigger out-of-bounds write and execute arbitrary code on the target system.

Exploitation example:

perl -e 'print "a id (\"foo\" \"".("x"x1021)."\\A\" \"bar\"
\"\000".("x"x1020)."\\A\")\n"' | nc localhost 143

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Dovecot: 2.2.0 - 2.3.7.1

External links

http://dovecot.org/pipermail/dovecot-news/2019-August/000418.html
http://github.com/dovecot/core/commit/85fcb895ca7f0bcb8ee72047fe0e1e78532ff90b
http://github.com/dovecot/core/commit/f904cbdfec25582bc5e2a7435bf82ff769f2526a
http://github.com/dovecot/pigeonhole/commit/7ce9990a5e6ba59e89b7fe1c07f574279aed922c
http://github.com/dovecot/pigeonhole/commit/4a299840cdb51f61f8d1ebc0210b19c40dfbc1cc

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

How the attacker can exploit this vulnerability?

The attacker would have to send a specially crafted request to the affected application in order to exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.