Man-in-the-Middle (MitM) attack in Exim - CVE-2021-38371
Published: March 20, 2023
Vulnerability identifier: #VU73857
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2021-38371
CWE-ID: CWE-300
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Exim
Affected software:
Exim
Exim
Detailed vulnerability description
The vulnerability allows a remote attacker to perform MitM attack.
The vulnerability exists due to the way Exim handles concurrent STARTTLS sessions when sending out emails. A malicious server can send a response to the *next* command within the existing STARTTLS sessions and force the Exim to treat this session as trusted.
How to mitigate CVE-2021-38371
Install updates from vendor's website.