No exploitation reportedFix available

CVE-2020-28021

Q: Is CVE-2020-28021 actively exploited?

Active exploitation of CVE-2020-28021 has not been confirmed. Its EPSS score was 4.1% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2020-28021?

CVE-2020-28021 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

No exploitation reported by the sources we read.

Published2021-05-06
Fixed in4.94.2

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 has Improper Neutralization of Line Delimiters. An authenticated remote SMTP client can insert newline characters into a spool file (which indirectly leads to remote code execution as root) via AUTH= in a MAIL FROM command.

Timeline

dates in UTC

2021-05-0613:15CVE publishedNVD

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-2020-28021?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2020-28021?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	≥ 4.00, < 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

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVSS 3.18.8read 2026-10-23
NVDCVSS 2.09read 2026-10-23
FIRST EPSSEPSS score4.1 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:L/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-2020-28021?

Is CVE-2020-28021 actively exploited?

Active exploitation of CVE-2020-28021 has not been confirmed. Its EPSS score was 4.1% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2020-28021?

CVE-2020-28021 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

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