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CVE-2018-6789

9.8, critical Known exploited Used in ransomware

Exim Buffer Overflow Vulnerability

NVD (opens in a new tab) CVE.org (opens in a new tab) CISA KEV catalogue (opens in a new tab)
CVSS
9.8, critical critical CVSS v3.1
EPSS, next 30 days
82% higher than 99.6% of scored CVEs
Exploitation
Confirmed in the wild
Published
8 Feb 20188 years ago

Known exploited

CISA added this to the Known Exploited Vulnerabilities Catalog on 3 Nov 2021 and links it to ransomware activity. US federal agencies had to remediate by 3 May 2022, a deadline that has passed.

Required action. Apply updates per vendor instructions.

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.

Details

Vendor
Exim and 2 more
Product
Exim
Weakness
CWE-120 (opens in a new tab)
Status
Analyzed
Updated
17 Jun 2026
Assigner
cve@mitre.org

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References 14

Exploit code 4

Patches and fixes 1

Advisories 8

Other references 1

The kind is read from NVD's tags where present and from the shape of the URL otherwise, so treat it as a hint.

Other Exim CVEs

Every Exim CVE we hold

Same vendor in what we hold, not a known link between the flaws.

  • CVE-2019-16928 Exim Out-of-bounds Write Vulnerability KEV EPSS 42% 9.8, critical
  • CVE-2019-10149 Exim Mail Transfer Agent (MTA) Improper Input Validation KEV EPSS 100% 9.8, critical
  • CVE-2010-4344 Exim Heap-Based Buffer Overflow Vulnerability KEV EPSS 72% 9.8, critical
  • CVE-2010-4345 Exim Privilege Escalation Vulnerability KEV EPSS 18% 7.8, high
  • CVE-2026-94056 Exim before 4.100.1, when Proxy-Protocol is used with an attacker-controlled proxy, allows attackers to read certain uninitialized data… EPSS 0.2% 7.5, high

Beyond this page

Is CVE-2018-6789 in your network?

This page tells you how dangerous CVE-2018-6789 is out there. Whether it sits on one of your devices, only a scan of your own network can tell. That is what our systems do, every day, for the companies we protect.

CVE-2018-6789 is in the CISA catalogue of exploited vulnerabilities: attackers are already exploiting it.

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  • EXYS7950 KONDRA

    Detect it if it's exploited

    Until the patch is applied, Kondra monitors your network, events and endpoints in real time. It keeps an inventory of the software installed on every endpoint, and its anomaly detection rules flag what an attacker does once inside.

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Check your exposure

Assembled from the NVD 2.0 API, the CISA Known Exploited Vulnerabilities Catalog and FIRST EPSS. Scores are as of our last collection on 16 Oct 2026, not the live upstream state.