CVE-2020-28024 Memory corruption in n/a

Critical 9.8 Published 6 May 2021 Updated 4 Aug 2024

Unauthenticated remote attackers can execute arbitrary commands on Exim mail servers due to a buffer underwrite vulnerability in the SMTP input handling.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2020-28024?

CVE-2020-28024 is a critical memory corruption vulnerability in Exim Exim, published on 6 May 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Exim 4 before 4.94.2 allows Buffer Underwrite that may result in unauthenticated remote attackers executing arbitrary commands, because smtp_ungetc was only intended to push back characters, but can actually push back non-character error codes such as EOF.

Weakness: CWE-787

Which versions are affected by CVE-2020-28024?

It affects 1 product.

Products include Exim Exim.

How do I fix CVE-2020-28024?

Upgrade to a fixed version.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2020-28024 being exploited?

There is no known exploitation of CVE-2020-28024 in the wild and no public exploit code.

All Exim Exim vulnerabilities

Sources

Also known as CLEANSTART-2025-XC94447, DEBIAN-CVE-2020-28024, GHSA-4wmr-6rg6-hfcg, UBUNTU-CVE-2020-28024.