CVE-2018-6789: Exim Buffer Overflow Vulnerability

Critical severity, CVSS 9.8. Actively exploited: in CISA KEV since 2021-11-03. EPSS: 82.1% chance of exploitation in the next 30 days.

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.

Affected products

• Canonical Ubuntu Linux: version 14.04 only; version 16.04 only; version 17.10 only
• Debian Debian Linux: version 7.0 only; version 8.0 only; version 9.0 only
• Exim Exim: before 4.90.1 (fixed in 4.90.1)

Published 2018-02-08. Last modified 2026-06-17.