CVE-2020-28026Public exploitNetwork attack vector

Root command execution via truncated spool header

Published May 6, 2021 · Updated Aug 4, 2024

Line injection in Exim before 4.94.2 allows remote attackers to execute arbitrary commands as root through a crafted SMTP ORCPT parameter. The second recipient-reading loop in spool_read_header() uses a fixed 16 KB buffer, causing a longer ORCPT-derived spool record to be truncated and its remainder parsed as a separate header line. This unauthenticated path is reachable only when DSN is enabled, which is not the default, and successful exploitation grants root command execution.

CVSS severity9.8
Critical
EPSS probability9.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Line injection in Exim before 4.94.2 allows remote attackers to execute arbitrary commands as root through a crafted SMTP ORCPT parameter. The second recipient-reading loop in spool_read_header() uses a fixed 16 KB buffer, causing a longer ORCPT-derived spool record to be truncated and its remainder parsed as a separate header line. This unauthenticated path is reachable only when DSN is enabled, which is not the default, and successful exploitation grants root command execution.

The record

CVE
CVE-2020-28026
Published
May 6, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.3NIST NVDAV:N/AC:M/Au:N/C:C/I:C/A:C
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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