Ubuntu update for OpenSMTPD

Published: 2020-03-03

Risk	Medium
Patch available	YES
Number of vulnerabilities	2
CVE-ID	CVE-2020-8794 CVE-2020-8793
CWE-ID	CWE-125 CWE-264
Exploitation vector	Network
Public exploit	Public exploit code for vulnerability #1 is available. Public exploit code for vulnerability #2 is available.
Vulnerable software Subscribe	opensmtpd (Ubuntu package) Operating systems & Components / Operating system package or component
Vendor	Canonical Ltd.

Security Bulletin

This security bulletin contains information about 2 vulnerabilities.

1) Out-of-bounds read

EUVDB-ID: #VU25625

Risk: Medium

CVSSv3.1: 6 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N/E:F/RL:O/RC:C]

CVE-ID: CVE-2020-8794

CWE-ID: CWE-125 - Out-of-bounds read

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to gain access to potentially sensitive information.

The vulnerability exists due to a boundary condition in mta_io() function in mta_session.c for multi-line replies during mail delivery. A remote attacker can use a mail server to send specially crafted replies, trigger out-of-bounds read error and read contents of memory on the system.

Mitigation

Update the affected packages.

Ubuntu 19.10: opensmtpd - 6.0.3p1-6ubuntu0.2
Ubuntu 18.04 LTS: opensmtpd - 6.0.3p1-1ubuntu0.2

Vulnerable software versions

opensmtpd (Ubuntu package): 6.0.2p1-1 - 6.0.3p1-6ubuntu0.1

External links

http://usn.ubuntu.com/4294-1/

Q & A

Can this vulnerability be exploited remotely?

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

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, a fully functional exploit for this vulnerability is available.

2) Permissions, Privileges, and Access Controls

EUVDB-ID: #VU25586

Risk: Low

CVSSv3.1: 7.9 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2020-8793

CWE-ID: CWE-264 - Permissions, Privileges, and Access Controls

Exploit availability: Yes

Description

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to the application does not drop privileges when executing the "/usr/sbin/smtpctl" application with a "-bi" command-line argument. A local user can leverage this behavior and use a specially crafted hardlink to execute arbitrary code on the system with elevated privileges.

Mitigation

Update the affected packages.

Ubuntu 19.10: opensmtpd - 6.0.3p1-6ubuntu0.2
Ubuntu 18.04 LTS: opensmtpd - 6.0.3p1-1ubuntu0.2

Vulnerable software versions

opensmtpd (Ubuntu package): 6.0.2p1-1 - 6.0.3p1-6ubuntu0.1

External links

http://usn.ubuntu.com/4294-1/

Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

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.