Overview:
A series of critical vulnerabilities were recently disclosed to reside in the popular internet mailer, Exim. The vulnerabilities, collectively termed as 21Nails, were brought to light by researchers at Qualys. The advisory includes 21 vulnerabilities, some of which can be used to gain elevated privileges on the affected systems and perform remote code execution.

CVEs assigned
CVE-2020-28007
CVE-2020-28008
CVE-2020-28009
CVE-2020-28010
CVE-2020-28011
CVE-2020-28012
CVE-2020-28013
CVE-2020-28014
CVE-2020-28015
CVE-2020-28016
CVE-2020-28017
CVE-2020-28018
CVE-2020-28019
CVE-2020-28020
CVE-2020-28021
CVE-2020-28022
CVE-2020-28023
CVE-2020-28024
CVE-2020-28025
CVE-2020-28026
CVE-2021-27216

Affected software:
Exim versions before 4.94.2 are affected.

Solution:
To address this vulnerability, the vendor has released security patches. For more information, please refer to our blog
Use SanerNow platform to apply this critical patch quickly across the organization as shown below.

SanerNow: Vulnerability detection and patching of 21Nails vulnerability:
1. Login to SanerNow platform
2. Switch to the account/site specific view and Go to 'VM tool'
3. If your Linux Operating System is vulnerable, Saner lists the above CVE’s ('CVE-2020-28007' and others) in 'Top Vulnerabilities' or 'Recently Discovered Vulnerabilities' as shown in the below diagram

4. Search for this vulnerability in the VM tool. If you are affected, apply the patch through PM -> Missing Patches
5. Select 'Groups/Devices' in the 'Asset Source' section and click 'Apply'.
6. Select the 'exim4' product from the 'Asset' section as shown in the below diagram.

7. Select 'Apply Selected Patches' at the rightmost corner. This will prompt for 'Creating Patching Task'. Fill in 'Task Name' and 'Remediation Schedule' as per your preference and click on 'Apply Selected Patches' as shown below,

8. Remediation job will be created, which will fix the vulnerability by upgrading the software and making the system immune to Exim vulnerabilities.
9. Once remediation is done, the Saner agent automatically scans again and upload the result to SanerNow as shown below.