CVE-2023-42116 Exim SMTP Challenge Stack-based Buffer Overflow Remote Code Execution Vulnerability
Remote attackers can execute arbitrary code on Exim mail servers via a stack-based buffer overflow in NTLM challenge handling without authentication.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-42116?
CVE-2023-42116 is a high-severity memory corruption vulnerability in Exim Exim, published on 3 May 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Exim SMTP Challenge Stack-based Buffer Overflow Remote Code Execution Vulnerability. This vulnerability allows remote attackers to execute arbitrary code on affected installations of Exim. Authentication is not required to exploit this vulnerability.
The specific flaw exists within the handling of NTLM challenge requests. The issue results from the lack of proper validation of the length of user-supplied data prior to copying it to a fixed-length stack-based buffer. An attacker can leverage this vulnerability to execute code in the context of the service account. . Was ZDI-CAN-17515.
Weakness: CWE-121
Which versions are affected by CVE-2023-42116?
It affects 1 product.
Products include Exim Exim.
How do I fix CVE-2023-42116?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2023-42116 being exploited?
There is no known exploitation of CVE-2023-42116 in the wild and no public exploit code.
Other vulnerabilities in Exim Exim
Sources
Also known as CLEANSTART-2025-PP73466, DEBIAN-CVE-2023-42116, GHSA-5hxx-p89v-jxc7, UBUNTU-CVE-2023-42116.