CVE-2023-42117
Published: 03 May 2024
Summary
CVE-2023-42117 is a critical-severity Improper Neutralization of Special Elements (CWE-138) vulnerability in Exim Exim. Its CVSS base score is 9.8 (Critical).
Operationally, ranked in the top 8.1% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
Deeper analysis
CVE-2023-42117 is an improper neutralization of special elements vulnerability in Exim that leads to remote code execution. It affects the SMTP service listening on TCP port 25 and stems from insufficient validation of user-supplied data, resulting in a memory corruption condition that allows arbitrary code execution in the context of the Exim process. The issue was originally reported as ZDI-CAN-17554 and carries a CVSS 3.1 base score of 9.8.
Remote, unauthenticated attackers can exploit the flaw over the network by sending crafted input to the SMTP service, achieving code execution without any user interaction or privileges. The vulnerability impacts any exposed Exim installation that has not been patched.
Advisories from the Zero Day Initiative (ZDI-23-1471) and Debian LTS detail the issue and direct administrators to updated Exim packages.
The EPSS score rose from a low baseline to a peak of 0.1090 on 2025-12-11 before receding, indicating that exploitation interest increased after public disclosure.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2023-46576
Vulnerability details
Exim Improper Neutralization of Special Elements 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 smtp service,…
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which listens on TCP port 25 by default. The issue results from the lack of proper validation of user-supplied data, which can result in a memory corruption condition. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-17554.
- CWE(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
No mitigating controls mapped yet. The per-CVE control annotator has not reached this CVE.