CVE intelligence and bounded remediation

CVE-2020-12517 — Phoenixcontact Plcnext Firmware security vulnerability

Critical CVSS 9

On Phoenix Contact PLCnext Control Devices versions before 2021.0 LTS an authenticated low privileged user could embed malicious Javascript code to gain admin rights when the admin user visits the vulnerable website (local privilege escalation).

Severity
Critical
CVSS
9 (3.1)
Published
2020-12-17
CISA KEV
Not currently listed
Ecosystem
operating-system
Weaknesses
CWE-79

Affected products

  • phoenixcontact / plcnext_firmware

Showing 1 representative product identities from 6 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

Matched remediation archetype

Cross-site scripting and unsafe browser output

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Check exposure

  • Trace reflected, stored, and DOM-derived untrusted values into HTML, attributes, URLs, styles, scripts, and client-side template sinks.
  • Identify affected origins, authenticated user roles, sensitive browser capabilities, and where content is shared across tenants.
  • Review framework escaping, rich-text sanitization, legacy templates, and client-side rendering paths.

Remediate safely

  • Use context-aware framework output encoding and safe DOM APIs; keep untrusted data out of executable contexts.
  • Sanitize intentionally supported markup with a maintained allowlist policy and validate URLs and attributes separately.
  • Update affected rendering components and add tests for every output context using inert sentinel markup.

Authoritative sources

Complete CVE record and remediation plan

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