#VU52866 Input validation error in Exim - CVE-2020-28021

Vulnerability identifier: #VU52866

Vulnerability risk: Medium

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2020-28021

CWE-ID: CWE-20

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Exim
Server applications / Mail servers

Vendor: Exim

Description

The vulnerability allows a remote attacker to bypass implemented security restrictions

The vulnerability exists due to insufficient validation of user-supplied input when processing new line characters. A remote attacker can inject a new line character into the spool header file and modify the mail queue.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Exim: 4.00 - 4.94.1

---

External links
https://seclists.org/oss-sec/2021/q2/91

---

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.