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ExploitedIn CISA KEVFix available

CVE-2018-6789

Exploitation confirmed. First attested on 2021-11-03 by CISA-ADP, CISA KEV, GCVE · kevintel.

  • Published2018-02-08
  • WeaknessCWE-120

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2018-02-0823:29CVE publishedNVD
  2. 2021-11-03Listed as exploited by GCVEGCVE
  3. 2021-11-03Exploitation first reportedCISA KEV
  4. 2021-11-03Added to the CISA KEV catalogCISA KEV
  5. 2025-02-0714:03SSVC exploitation set to activeCISA-ADP
  6. 2026-10-2319:23First public proof of conceptPoC-in-GitHub
  7. 2026-10-2319:23EPSS crossed 10 %FIRST EPSS

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2018-6789?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2018-6789?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Canonical ubuntu linux
BranchAffectedFixed in
14.4= 14.04no fix published
16.4= 16.04no fix published
17.10= 17.10no fix published
Debian debian linux
BranchAffectedFixed in
7.0= 7.0no fix published
8.0= 8.0no fix published
9.0= 9.0no fix published
Exim
BranchAffectedFixed in
4.90< 4.90.14.90.1

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. CISA’s required action: Apply updates per vendor instructions.due 2022-05-03

Advisories and patches

Detection

read 2026-10-23 19:23 UTC
Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
5 repositories, unverifiedc0llision/exim-vuln-pocberaphin/CVE-2018-6789synacktiv/Exim-CVE-2018-6789martinclauss/exim-rce-cve-2018-6789thistehneisen/CVE-2018-6789-Python3
PoC-in-GitHub

CISA Known Exploited Vulnerability

Date Added
2021-11-03
Patch Due Date
2022-05-03
Ransomware Use
Known
Required Action
Apply updates per vendor instructions.

Sources

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2018-02-08
Last Modified
2026-06-17
NVD status
Analyzed

Frequently asked questions

What is CVE-2018-6789?

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.

Is CVE-2018-6789 actively exploited?

Yes. CVE-2018-6789 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, meaning it has been confirmed as actively exploited in the wild. CISA requires federal agencies to patch by 2022-05-03.

What is the CVSS score for CVE-2018-6789?

CVE-2018-6789 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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