CVE intelligence and bounded remediation

CVE-2020-7247 — OpenSMTPD Remote Code Execution Vulnerability

Critical CVSS 9.8 CISA KEV

smtp_mailaddr in smtp_session.c in OpenSMTPD 6.6, as used in OpenBSD 6.6 and other products, allows remote attackers to execute arbitrary commands as root via a crafted SMTP session, as demonstrated by shell metacharacters in a MAIL FROM field. This affects the "uncommented" default configuration. The issue exists because of an incorrect return value upon failure of input validation.

Severity
Critical
CVSS
9.8 (3.1)
Published
2020-01-29
CISA KEV
Known exploited
Ecosystem
software/application
Weaknesses
CWE-78, CWE-755

Affected products

  • openbsd / opensmtpd / 6.6
  • debian / debian_linux / 9.0
  • debian / debian_linux / 10.0
  • fedoraproject / fedora / 32
  • canonical / ubuntu_linux / 18.04
  • canonical / ubuntu_linux / 19.10

Matched remediation archetype

Command, code, expression, and template injection

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Check exposure

  • Trace untrusted values to process execution, interpreters, evaluators, template engines, dynamic imports, and administrative scripting features.
  • Determine whether the affected path is reachable across each trust boundary and which service account or host privilege it inherits.
  • Review configuration for optional execution features, unsafe compatibility modes, and shell invocation.

Remediate safely

  • Replace string-built commands or evaluated code with fixed operations and structured argument APIs that do not invoke a shell.
  • Use strict allowlists for operation identifiers and reject unexpected input before it reaches any interpreter.
  • Update the affected component and add inert regression tests covering metacharacters, encoding variants, and alternate request paths.

Authoritative sources

Complete CVE record and remediation plan

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