CVE-2020-28021

CVE-2020-28021 is a high-severity vulnerability in Exim with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

• Severity: High (CVSS 3.x base score 8.8)
• CVSS v2: 9.0
• EPSS exploit prediction: 4% (89th percentile)
• Actively exploited: Not listed in CISA KEV
• Affected product: Exim
• Published: 2021-05-06
• Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2020-28021?

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.

How severe is CVE-2020-28021?

CVE-2020-28021 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2020-28021 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (89th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-28021?

CVE-2020-28021 affects Exim. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-28021?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2020-28021 published?

CVE-2020-28021 was published on 2021-05-06 and last updated on 2026-06-17.

References

• https://www.exim.org/static/doc/security/CVE-2020-qualys/CVE-2020-28021-MAUTH.txt

Affected products (1)

• cpe:2.3:a:exim:exim:*:*:*:*:*:*:*:*

More vulnerabilities in Exim

• CVE-2026-45185 — Critical (CVSS 9.8): Exim before 4.99.3, in certain GnuTLS configurations, has a remotely reachable use-after-free in the BDAT body parsing…
• CVE-2023-42117 — Critical (CVSS 9.8): Exim Improper Neutralization of Special Elements Remote Code Execution Vulnerability. This vulnerability allows remote…
• CVE-2023-42116 — Critical (CVSS 9.8): Exim SMTP Challenge Stack-based Buffer Overflow Remote Code Execution Vulnerability. This vulnerability allows remote…
• CVE-2023-42115 — Critical (CVSS 9.8): Exim AUTH Out-Of-Bounds Write Remote Code Execution Vulnerability. This vulnerability allows remote attackers to…
• CVE-2022-37452 — Critical (CVSS 9.8): Exim before 4.95 has a heap-based buffer overflow for the alias list in host_name_lookup in host.c when…
• CVE-2020-28026 — Critical (CVSS 9.8): Exim 4 before 4.94.2 has Improper Neutralization of Line Delimiters, relevant in non-default configurations that enable…

All CVEs affecting Exim →

Threat intelligence

Threat-intel indicators referencing this CVE:

• 76.12.128.249 (ipv4-addr)
• 50.116.72.139 (ipv4-addr)
• 166.62.41.190 (ipv4-addr)
• 132.148.155.138 (ipv4-addr)
• 50.62.22.47 (ipv4-addr)
• 31.131.22.122 (ipv4-addr)
• 193.68.57.43 (ipv4-addr)
• 192.169.201.223 (ipv4-addr)