Public proof of conceptFix available

CVE-2020-28018

Q: Is CVE-2020-28018 actively exploited?

Active exploitation of CVE-2020-28018 has not been confirmed. Its EPSS score was 56.5% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2020-28018?

CVE-2020-28018 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.

A public proof of concept exists; no exploitation attested.

Published2021-05-06
Fixed in4.94.2
WeaknessCWE-416

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

Exim 4 before 4.94.2 allows Use After Free in smtp_reset in certain situations that may be common for builds with OpenSSL.

Timeline

dates in UTC

2021-05-0613:15CVE publishedNVD
2026-10-2319:23First public proof of conceptPoC-in-GitHub
2026-10-2319:23EPSS crossed 10 %FIRST EPSS

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 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-2020-28018?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2020-28018?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Exim

Branch	Affected	Fixed in	Source
4.x	≥ 4.90, < 4.94.2	4.94.2	NVD

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

Fix

Update Exim to 4.94.2

Advisories and patches

www.exim.orgVendor Advisory

Detection

read 2026-10-23 19:23 UTC

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: 1 repository, unverifieddorkerdevil/CVE-2020-28018

Sources

NVDCVSS 3.19.8read 2026-10-23
NVDCVSS 2.07.5read 2026-10-23
NVDweakness (CWE)CWE-416read 2026-10-23
FIRST EPSSEPSS score56.5 %read 2026-10-23
PoC-in-GitHubproof of concept1read 2026-10-23

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: 2021-05-06
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2020-28018?

Exim 4 before 4.94.2 allows Use After Free in smtp_reset in certain situations that may be common for builds with OpenSSL.

Is CVE-2020-28018 actively exploited?

Active exploitation of CVE-2020-28018 has not been confirmed. Its EPSS score was 56.5% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2020-28018?

CVE-2020-28018 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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