Improper Certificate Revocation Check (CVE‑2026‑9636) in Rockwell Automation CompactLogix & ControlLogix Modules Enables DoS
What It Is – A vulnerability in Rockwell Automation’s CompactLogix 5380, ControlLogix 5580 and EN4TR communication modules (CVE‑2026‑9636) causes the controller to ignore revoked intermediate certificates. An attacker who can present such a certificate can force a denial‑of‑service condition.
Exploitability – No public exploit code has been released, but the advisory notes that network‑based attackers can reliably trigger the flaw. CVSS v3 base score 5.9 (Moderate).
Affected Products – Rockwell Automation CompactLogix 5380, ControlLogix 5580, GuardLogix 5580, Compact GuardLogix 5380, and EN4TR V6.001/V7.001 modules (firmware versions V36‑V37).
Why It Matters for Compliance & Audit Readiness
- Control‑mapping: SOC 2 CC6.1 (system operations) and CC6.2 (change management) require documented, enforceable certificate‑validation processes; this flaw shows a gap that must be mapped and remediated.
- Continuous evidence: Demonstrating that CRL checks are enforced in real‑time provides audit‑ready evidence and reduces the risk of service‑disruption findings during a SOC 2 audit.
- Due‑diligence for third‑party risk: Many manufacturers rely on Rockwell controllers as a critical component of their supply chain; proving that you’ve validated and patched these devices is essential for vendor‑risk programs.
Recommended Actions
- Inventory all Rockwell CompactLogix/ControlLogix/EN4TR devices and confirm firmware version.
- Apply the vendor‑released patch that corrects the certificate‑revocation handling (or upgrade to a version > V37).
- Update your SOC 2 control map to include “Certificate Revocation List verification” under system operations.
- Capture remediation evidence (patch logs, configuration snapshots) in a centralized compliance repository.
- Enable continuous monitoring of certificate validation failures and feed alerts into your audit‑readiness dashboard.
Source: CISA Advisory – ICSA‑26‑211‑05