Exploited CVEs / Exim / CVE-2018-6789
CVE-2018-6789
Exim Buffer Overflow Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted, and the vulnerability is known to be used in ransomware campaigns. Federal agencies were required to remediate by 2022-05-03 (that deadline has passed); treat that date as the outer bound for your own environment. Check the vendor security advisory for the fix.
Risk summary
Actively exploited Exim vulnerability, Critical severity, CVSS 9.8. Added to the CISA KEV catalog 2021-11-03.
Senserva AI Opinion for CVE-2018-6789
Exim's base64 decoder in the SMTP listener overflows a buffer one byte at a time into remote code execution, and since Exim runs the mail service on a huge share of internet-facing Linux servers, worms and ransomware-linked campaigns adopted it readily. Critical Severity at CVSS 9.8 with an 82 percent EPSS score. Mail servers are internet-exposed by definition, so unpatched Exim is a standing invitation.
Do this: Check Exim versions on all Linux mail servers and upgrade any pre-4.90.1 build without waiting for a maintenance window.
AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for CVE-2018-6789
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Updated August 14, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.
Full tracking and change history for CVE-2018-6789
- Published
- 2021-11-03
- Last revised
- 2021-11-03
- Changes tracked
- 1
Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.
Drawn by Senserva Vivid from the Senserva change record. Hover any point for its date and value.
- 2021-11-03 added to the CISA KEV catalog by CISA
- 2026-07-17 CVSS 0.0 to 9.8; EPSS first scored at 82.2%
- 2026-07-23 EPSS 82.2% to 82.1%
- 2026-08-02 EPSS 82.1% to 81.7%
Recorded by Senserva on the dates shown, from CISA KEV and FIRST EPSS. This is what moved and when, which neither the vendor advisory nor NVD publishes.
CISA required action
Federal (BOD 22-01) remediation due date: 2022-05-03 (past due).
Apply updates per vendor instructions.
Official fix for CVE-2018-6789
Check the vendor's security advisory channel for the patched Exim versions and workarounds.
Common questions about CVE-2018-6789
Is CVE-2018-6789 actively exploited?
Yes. CVE-2018-6789 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2021-11-03, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 82%. CISA also reports it is known to be used in ransomware campaigns.
What is the CISA deadline and required action for CVE-2018-6789?
CISA set the federal (BOD 22-01) remediation due date at 2022-05-03, which has passed; treat any unremediated system as overdue. The verbatim required action: Apply updates per vendor instructions.
What fixes CVE-2018-6789?
Check the vendor's security advisory for the patched Exim versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.
Can I ask my own AI about CVE-2018-6789?
Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2018-6789's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).
Scope and sources
- More exploited Exim CVEs
All Exim exploited CVEs on one page: Exim vulnerabilities actively exploited.
- Authoritative references
Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.