Input validation error in Exim - CVE-2020-28021

Vulnerability identifier: #VU52866

CSH Severity: Medium

CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2020-28021

CWE-ID: CWE-20

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to bypass implemented security restrictions

The vulnerability exists due to insufficient validation of user-supplied input when processing new line characters. A remote attacker can inject a new line character into the spool header file and modify the mail queue.

Exim
Gentoo Linux
Amazon Linux AMI
Ubuntu
exim4 (Debian package)
exim4-base (Ubuntu package)
exim4-daemon-heavy (Ubuntu package)
exim4-daemon-light (Ubuntu package)

Install updates from vendor's website.

Exim - update to 4.94.2
exim4 (Debian package) - update to 4.92-8+deb10u6
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

• http://seclists.org/oss-sec/2021/q2/91

• Multiple vulnerabilities in Exim
• Gentoo update for Exim
• Debian update for exim4
• Amazon Linux AMI update for exim
• Ubuntu update for exim4