CVE-2020-8794

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 88.9% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2020-02-25 · updated 2026-06-17
Weakness: CWE-125

Description

OpenSMTPD before 6.6.4 allows remote code execution because of an out-of-bounds read in mta_io in mta_session.c for multi-line replies. Although this vulnerability affects the client side of OpenSMTPD, it is possible to attack a server because the server code launches the client code during bounce handling.

Affected products

Canonical Ubuntu Linux: 18.04, 19.10
Debian Linux: 9.0, 10.0
Fedoraproject Fedora: 31, 32
Opensmtpd: before 6.6.4 — fixed in 6.6.4

How to fix

Upgrade to a fixed version: Opensmtpd 6.6.4. Check the vendor advisory for mitigations.

References

http://packetstormsecurity.com/files/156633/OpenSMTPD-Out-Of-Bounds-Read-Local-Privilege-Escalation.html
http://seclists.org/fulldisclosure/2020/Feb/32
http://www.openwall.com/lists/oss-security/2020/02/26/1
http://www.openwall.com/lists/oss-security/2020/03/01/1
http://www.openwall.com/lists/oss-security/2020/03/01/2
http://www.openwall.com/lists/oss-security/2021/05/04/7
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OPH4QU4DNVHA7ACFXMYFCEP5PSXXPN4E/
https://usn.ubuntu.com/4294-1/
https://www.debian.org/security/2020/dsa-4634
https://www.openbsd.org/security.html
https://www.openwall.com/lists/oss-security/2020/02/24/5
http://packetstormsecurity.com/files/156633/OpenSMTPD-Out-Of-Bounds-Read-Local-Privilege-Escalation.html

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