CVE-2018-6789 Exim Buffer Overflow

What is CVE-2018-6789?

CVE-2018-6789 is a critical memory corruption vulnerability in Canonical Ubuntu Linux, published on 8 Feb 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

An issue was discovered in the base64d function in the SMTP listener in Exim before 4.90.1. By sending a handcrafted message, a buffer overflow may happen. This can be used to execute code remotely.

Weakness: CWE-120

Which versions are affected by CVE-2018-6789?

It affects 3 products.

Products include Canonical Ubuntu Linux, Debian Debian Linux, Exim Exim.

How do I fix CVE-2018-6789?

Upgrade to a fixed version. US federal agencies must fix it by 3 May 2022.

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

Is CVE-2018-6789 being exploited?

Yes. Attackers have exploited CVE-2018-6789 in the wild since at least 3 Nov 2021, including in ransomware campaigns.

Public exploit code: 2 Exploit-DB entries and 5 proofs of concept on GitHub.

Other vulnerabilities in Canonical Ubuntu Linux

• CVE-2020-11651 SaltStack Salt Authentication Bypass Exploited Critical 9.8
• CVE-2020-7247 OpenSMTPD Remote Code Execution Exploited Critical 9.8
• CVE-2019-16928 Exim Out-of-bounds Write Exploited Critical 9.8
• CVE-2015-2590 Oracle Java SE and Java SE Embedded Remote Code Execution Exploited Critical 9.8
• CVE-2013-0422 Oracle JRE Remote Code Execution Exploited Critical 9.8

All Canonical Ubuntu Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as CLEANSTART-2025-AY16629, DEBIAN-CVE-2018-6789, DLA-1274-1, DSA-4110-1, GHSA-868p-wr6f-7jfr, UBUNTU-CVE-2018-6789 and 1 more.