Exim Vulnerability Affecting Public Email Servers

A vulnerability affecting the Exim mail transfer agent (MTA) exposes 56% of all publicly available email servers to remote code execution or denial-of-service (DoS) attacks.

Threat ID:: CC-1836
Category:: Exploit
Threat Severity:: Low
Threat Vector:
Published:: 6 December 2017 12:00 AM

Report a cyber attack: call 0300 303 5222 or email [email protected]

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Summary

A vulnerability affecting the Exim mail transfer agent (MTA) exposes 56% of all publicly available email servers to remote code execution or denial-of-service (DoS) attacks.

Affected platforms

The following platforms are known to be affected:

Exim

Exim Mail Transfer Agent - Versions prior to 4.89.1

Threat details

An error in the way Exim parses BDAT (an alternative to the Simple Mail Transfer protocol DATA command) data headers affects how the MTA manages “chunking”; or breaking down, handling and reconstructing emails. An attacker may exploit this by tampering with the header, which can lead to the MTA reading from other memory locations. This can result in remote code execution.

Remediation steps

Type	Step
	Administrators are encouraged to review Exim Update 4.89.1 and apply the patch. Alternatively, if the patch is unable to be applied, a workaround has been provided by Exim.

Last edited: 17 February 2020 11:30 am