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Vulnerability in OpenSMTPD Could Allow for Remote Code Execution

MS-ISAC ADVISORY NUMBER:

2020-026

DATE(S) ISSUED:

02/26/2020

OVERVIEW:

A vulnerability has been discovered in OpenSMTPD which would allow for remote code execution and local privilege escalation. OpenSMTPD is an open-source server-side implementation of the Simple Mail Transfer Protocol (SMTP) that is part of the OpenBSD Project. A remote attacker could exploit this vulnerability to execute arbitrary code in the context of the server.

THREAT INTELLIGENCE:

Qualys, Inc. currently has an unreleased exploit for CVE-2020-8794.

SYSTEMS AFFECTED:

  • OpenSMTPD 5.9 – 6.6.3p1

RISK:

Government:
  • Large and medium government entities: HIGH
  • Small government entities: MEDIUM
Businesses:
  • Large and medium business entities: HIGH
  • Small business entities: MEDIUM
Home Users:
LOW

TECHNICAL SUMMARY:

A vulnerability has been discovered in OpenSMTPD which could allow for arbitrary code execution. An out of bounds read in smtpd allows an attacker to inject arbitrary commands into the envelope file which are then executed as root. Separately, missing privilege revocation in smtpctl allows arbitrary commands to be run with the _smtpq group. Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code in the context of the server.

RECOMMENDATIONS:

We recommend the following actions be taken:

  • Apply the updates immediately after appropriate testing.
  • Run all software as a non-privileged user (one without administrative rights) to diminish the effects of a successful attack.
  • Remind all users not to visit untrusted websites or follow links provided by unknown or untrusted sources.
  • Inform and educate users regarding threats posed by hypertext links contained in emails or attachments especially from untrusted sources.
  • Apply the Principle of Least Privilege to all systems and services.

REFERENCES:

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