Use-after-free in Exim - CVE-2020-28018
Published: May 4, 2021 / Updated: October 14, 2021
Vulnerability identifier: #VU52871
CSH Severity: Critical
CVSS v4: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2020-28018
CWE-ID: CWE-416
Exploitation vector: Remote access
Exploit availability:
Public exploit is available
Vulnerability details
The vulnerability allows a remote attacker to compromise vulnerable system.
The vulnerability exists due to a use-after-free error in tls-openssl.c. A remote non-authenticated attacker can send specially crafted data to the mail server, trigger a use-after-free error and execute arbitrary code on the system with root privileges.
Successful exploitation of the vulnerability may allow an attacker to compromise vulnerable system.
Affected software
Exim
Gentoo Linux
Amazon Linux AMI
Ubuntu
exim4-base (Ubuntu package)
exim4-daemon-heavy (Ubuntu package)
exim4-daemon-light (Ubuntu package)
Gentoo Linux
Amazon Linux AMI
Ubuntu
exim4-base (Ubuntu package)
exim4-daemon-heavy (Ubuntu package)
exim4-daemon-light (Ubuntu package)
How to mitigate CVE-2020-28018
Install updates from vendor's website.
Exim - update to 4.94.2
exim4-base (Ubuntu package) - addressed in versions 4.90.1-1ubuntu1.8, 4.93-13ubuntu1.5, 4.94-7ubuntu1.2, 4.94-15ubuntu1.2
exim4-daemon-heavy (Ubuntu package) - addressed in versions 4.90.1-1ubuntu1.8, 4.93-13ubuntu1.5, 4.94-7ubuntu1.2, 4.94-15ubuntu1.2
exim4-daemon-light (Ubuntu package) - addressed in versions 4.90.1-1ubuntu1.8, 4.93-13ubuntu1.5, 4.94-7ubuntu1.2, 4.94-15ubuntu1.2
exim4-base (Ubuntu package) - addressed in versions 4.90.1-1ubuntu1.8, 4.93-13ubuntu1.5, 4.94-7ubuntu1.2, 4.94-15ubuntu1.2
exim4-daemon-heavy (Ubuntu package) - addressed in versions 4.90.1-1ubuntu1.8, 4.93-13ubuntu1.5, 4.94-7ubuntu1.2, 4.94-15ubuntu1.2
exim4-daemon-light (Ubuntu package) - addressed in versions 4.90.1-1ubuntu1.8, 4.93-13ubuntu1.5, 4.94-7ubuntu1.2, 4.94-15ubuntu1.2