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Exim Buffer Overflow Vulnerability

A vulnerability in the Exim mail transfer agent (MTA) may allow an unauthenticated remote attacker to execute arbitrary code. Over 400,000 Exim servers are estimated to be vulnerable.
Threat ID:
CC-2130
Category:
Threat Severity:
Low
Threat Vector:
Published:
14 March 2018 12:00 AM
Report a cyber attack: call 0300 303 5222 or email [email protected]

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This article no longer conforms to NHS Digital's standards for cyber alerts, and may contain outdated or inaccurate information. Use of this information contained in this page is at your own risk

Summary

A vulnerability in the Exim mail transfer agent (MTA) may allow an unauthenticated remote attacker to execute arbitrary code. Over 400,000 Exim servers are estimated to be vulnerable.

Affected platforms

The following platforms are known to be affected:

Exim

  • Exim MTA - Versions 4.90 and earlier

Threat details

An error in the decode buffer length calculation used by Exim an be exploited by sending a specially crafted message to the targeted device, This then causes a buffer overflow condition which the attacker can used to insert new data into the memory space vacated by the overflow. This new data can be contain commands to access the access control list (ACL) strings. By then resetting the buffer this data, including the ACL strings, is released at which point the attacker can alter the ACL.

For further information:

Remediation steps

Type Step
At the time of publication, Exim have confirmed a patch is due for release once testing has been completed. Administrator's are encouraged to update in line with their standard patching regime as soon as this is available.

CVE Vulnerabilities

Status

CVE-2018-6789

Last edited: 17 February 2020 12:42 pm