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CVE-2020-8794 is a critical vulnerability in OpenSMTPD (before 6.6.4) due to an out-of-bounds read in the mta_io function in mta_session.c, specifically when handling multi-line SMTP replies. The flaw, introduced in December 2015, allows remote attackers to execute arbitrary shell commands, potentially as root, in the default configuration. Although the vulnerability is in client-side code, it can be exploited on the server during bounce handling, as the server launches the client code. The vulnerability is triggered by maliciously crafted multi-line SMTP responses, allowing attackers to inject arbitrary lines into OpenSMTPD's mail envelope and achieve command execution. Affected systems include OpenBSD 5.9–6.6, Debian 10/11, and Fedora 31.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos (1 hidden).
This repository contains a single Metasploit module (Ruby file) that exploits CVE-2020-8794, a local privilege escalation vulnerability in OpenSMTPD (versions prior to 6.6.4) on Unix systems. The exploit abuses an out-of-bounds read in OpenSMTPD's MTA implementation to execute arbitrary commands as either the root or nobody user, depending on the grammar version used by OpenSMTPD. The module sets up a fake SMTP server, crafts a malicious SMTP message, and uses the local sendmail binary to trigger the vulnerability. The default payload is a reverse shell (cmd/unix/reverse_netcat), but any command payload can be used. The exploit requires local access to the target system and a running, vulnerable OpenSMTPD service. The code is operational and ready for use within the Metasploit framework.
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