Multiple vulnerabilities in OpenSMTPD

Published: 2020-12-29

Risk	Medium
Patch available	YES
Number of vulnerabilities	2
CVE-ID	CVE-2020-35680 CVE-2020-35679
CWE-ID	CWE-476 CWE-401
Exploitation vector	Network
Public exploit	N/A
Vulnerable software Subscribe	OpenSMTPD Server applications / Mail servers
Vendor	OpenBSD

Security Bulletin

This security bulletin contains information about 2 vulnerabilities.

1) NULL pointer dereference

EUVDB-ID: #VU49179

Risk: Medium

CVSSv3.1: 5.2 [CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2020-35680

CWE-ID: CWE-476 - NULL Pointer Dereference

Exploit availability: No

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to a NULL pointer dereference error in smtpd/lka_filter.c in certain configurations. A remote attacker can trigger denial of service conditions via a crafted pattern of client activity, because the filter state machine does not properly maintain the I/O channel between the SMTP engine and the filters layer.

Mitigation

Install update from vendor's website.

Vulnerable software versions

OpenSMTPD: 6.0.0 - 6.7.1p1

External links

http://github.com/openbsd/src/commit/6c3220444ed06b5796dedfd53a0f4becd903c0d1
http://poolp.org/posts/2020-12-24/december-2020-opensmtpd-6.8.0p1-released-fixed-several-bugs-proposed-several-diffs-book-is-on-github/
http://www.mail-archive.com/misc@opensmtpd.org/msg05188.html

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.

2) Memory leak

EUVDB-ID: #VU49180

Risk: Medium

CVSSv3.1: 6.5 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2020-35679

CWE-ID: CWE-401 - Missing release of memory after effective lifetime