CVE intelligence and bounded remediation

CVE-2019-5477 — Nokogiri Nokogiri security vulnerability

Critical CVSS 9.8

A command injection vulnerability in Nokogiri v1.10.3 and earlier allows commands to be executed in a subprocess via Ruby's `Kernel.open` method. Processes are vulnerable only if the undocumented method `Nokogiri::CSS::Tokenizer#load_file` is being called with unsafe user input as the filename. This vulnerability appears in code generated by the Rexical gem versions v1.0.6 and earlier. Rexical is used by Nokogiri to generate lexical scanner code for parsing CSS queries. The underlying vulnerability was addressed in Rexical v1.0.7 and Nokogiri upgraded to this version of Rexical in Nokogiri v1.10.4.

Severity
Critical
CVSS
9.8 (3.1)
Published
2019-08-16
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-78

Affected products

  • nokogiri / nokogiri
  • canonical / ubuntu_linux / 16.04
  • canonical / ubuntu_linux / 18.04
  • canonical / ubuntu_linux / 19.04
  • canonical / ubuntu_linux / 19.10
  • debian / debian_linux / 8.0

Showing 6 representative product identities from 7 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

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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