CVE-2018-6789
Exim Buffer Overflow Vulnerability
- Critical 9.8
- Exploited: added to CISA KEV 3 Nov 2021
- Used in ransomware campaigns
- A public exploit reference is listed
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.
Key facts
- Published
- 8 Feb 2018
- Last changed
- 21 Oct 2025
- Assigned by
- mitre
- KEV added
- 3 Nov 2021
- KEV fix due
- 3 May 2022
- Used in ransomware
- Yes, according to CISA
- EPSS
- 82.137% likely to be exploited in the next 30 days, higher than 99.664% of CVEs (scores for 15 Nov 2026)
- SSVC (CISA)
- Exploitation: active; Automatable: yes; Technical impact: total
Severity scores
Each score is shown as its source gave it. They are not averaged or merged.
- 9.8CVSS 3.1, Criticalfrom CISA (ADP container)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
What to do
- Apply updates per vendor instructions.CISA KEV required action
Historical context and remediation
This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.
No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.
Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.
Affected products
| Vendor | Product | Versions |
|---|---|---|
| n/a | n/a |
|
Timeline
- 8 Feb 2018 Published
- 3 Nov 2021 CVE-2018-6789 added to CISA KEV
- 3 Nov 2021 Added to the CISA KEV catalogue