Exim < 4.89.1 Use-After-Free BDAT Remote Code Execution

critical Nessus Plugin ID 104815
New! Plugin Severity Now Using CVSS v3

The calculated severity for Plugins has been updated to use CVSS v3 by default. Plugins that do not have a CVSS v3 score will fall back to CVSS v2 for calculating severity. Severity display preferences can be toggled in the settings dropdown.

Synopsis

The remote mail server is potentially affected by a remote code execution flaw.

Description

According to its banner and supported extensions, the remote installation of Exim is affected by a code execution flaw. The implementation of the BDAT SMTP verb for sending large binary messages introduced in Exim 4.88 can incorrectly free an in-use region of memory, leading to memory corruption and potentially allowing an attacker to execute code.

Solution

Update to Exim 4.89.1 or later, or Exim 4.90-RC3 or later. If you cannot upgrade, edit your Exim configuration and set 'chunking_advertise_hosts' to an empty value as a workaround.

See Also

https://lists.exim.org/lurker/message/20171125.034842.d1d75cac.en.html

Plugin Details

Severity: Critical

ID: 104815

File Name: exim_bdat_chunk_uaf.nasl

Version: 1.5

Type: remote

Published: 11/29/2017

Updated: 11/12/2019

Dependencies: smtpserver_detect.nasl

Risk Information

CVSS Score Source: CVE-2017-16943

VPR

Risk Factor: Medium

Score: 5.9

CVSS v2

Risk Factor: High

Base Score: 7.5

Temporal Score: 5.5

Vector: AV:N/AC:L/Au:N/C:P/I:P/A:P

Temporal Vector: E:U/RL:OF/RC:C

CVSS v3

Risk Factor: Critical

Base Score: 9.8

Temporal Score: 8.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/a:exim:exim

Exploit Ease: No known exploits are available

Patch Publication Date: 11/29/2017

Vulnerability Publication Date: 11/24/2017

Reference Information

CVE: CVE-2017-16943