Remote root code execution vulnerability in Exim MTA

Reference:
Advisory #2019-021

Version:
1.0

Affected software:
Exim (all versions up to and including 4.92.1)

Type:
remote root code execution

CVE/CVSS:
CVE-2019-15846  

Sources

Official exim.org summary : https://www.exim.org/static/doc/security/CVE-2019-15846.txt

Initial alert to mailing lists : https://www.openwall.com/lists/oss-security/2019/09/04/1

The Register analysis : https://www.theregister.co.uk/2019/09/06/exim_vulnerability_patch/

Risks

An attacker (local or remote) can execute arbitrary code with root privileges, possibly leading to compromise of system/data integrity, confidentiality, and/or availability.

Description

The popular open-source MTA (mail transfer agent) Exim has a severe vulnerability (which is exploitable by sending a SNI ending in a backslash-null sequence during the initial TLS handshake.)

Although there has not yet been a CVSS score assigned, this is as bad as vulnerabilities get. While we have not yet received reports of this vulnerability being exploited in the wild, public proof-of-concept code exists so it is only a short matter of time until we see widespread exploitation of this vulnerability. 

Recommended Actions

CERT.be recommends to system administrators to patch your systems immediately if they are running Exim.

References

Additional technical details are available in the Exim GitHub repository here.