CVE-2026-1773 – IEC 60870-5-104 Denial of Service

Upon discovery or suspicion of compromise related to CVE-2026-1773, immediate actions are critical to contain the threat and prevent further damage.
1.1. Isolate Affected Systems: Immediately disconnect or segment any AcmeCorp Enterprise Portal (ACEP) instances running vulnerable versions (3.0.0 through 3.4.1) from public networks and internal critical infrastructure. This can involve firewall rules to block all inbound connections except from trusted administration hosts, or physically removing them from the network if necessary.
1.2. Review Access Logs: Scrutinize ACEP access logs, SAML assertion logs (if available), and underlying web server (e.g., Apache, Nginx, IIS) logs for any unusual or unauthorized authentication attempts, especially those preceding successful administrative logins from unknown IP addresses. Look for repeated attempts with malformed SAML requests or successful logins to administrative accounts from non-standard sources.
1.3. Force Password Resets for Administrative Accounts: As a precautionary measure, force a password reset for all administrative accounts within ACEP and any integrated identity providers. This helps mitigate risks if an attacker managed to establish persistence or compromise credentials post-bypass.
1.4. Disable SAML Authentication Temporarily: If the business critical nature of ACEP allows, temporarily disable SAML 2.0 authentication for the affected instances. Revert to a local authentication mechanism or a different identity provider if available and secure. This immediately closes the attack vector.
1.5. Backup Critical Data: Perform an immediate backup of all critical data and configurations associated with the ACEP instance. This ensures data recovery in case of further compromise or system instability during remediation.

2. PATCH AND UPDATE INFORMATION

The vendor, AcmeCorp, has released an emergency security patch to address CVE-2026-1773.
2.1. Affected Versions: AcmeCorp Enterprise Portal (ACEP) versions 3.0.0, 3.0.1, 3.1.0, 3.1.1, 3.2.0, 3.2.1, 3.3.0, 3.3.1, 3.4.0, and 3.4.1 are vulnerable.
2.2. Remediation Version: Upgrade to ACEP version 3.4.2 or later. This version contains the fix for the insufficient validation of the 'AuthnContextClassRef' element in the SAML handler.
2.3. Patch Application Instructions:
2.3.1. Obtain the patch: Download the official ACEP 3.4.2 (or latest) upgrade package from the AcmeCorp support portal. Do not use unofficial sources.
2.3.2. Review Release Notes: Carefully read the release notes for version 3.4.2 for any prerequisites, known issues, or specific upgrade steps pertinent to your environment.
2.3.3. Backup: Before commencing the upgrade, perform a full system backup of your ACEP instance, including application files, configuration files, and the underlying database.
2.3.4. Apply Upgrade: Follow the official AcmeCorp upgrade guide for your specific operating system and deployment type (e.g., standalone, clustered). Typically, this involves stopping the ACEP service, replacing application files, running database migration scripts if necessary, and restarting the service.
2.3.5. Verify Upgrade: After the upgrade, verify that the ACEP instance is running version 3.4.2 or higher. Test core functionalities, especially SAML authentication, to ensure proper operation.
2.4. Emergency Hotfix: For environments where a full version upgrade is not immediately feasible, AcmeCorp may offer a targeted hotfix for specific vulnerable versions. Consult AcmeCorp support for availability and application instructions for such hotfixes. Prioritize the full upgrade if possible.

3. MITIGATION STRATEGIES

While awaiting or applying patches, implement the following mitigation strategies to reduce the attack surface and impact of CVE-2026-1773.
3.1. Web Application Firewall (WAF) Rules: Deploy or update WAF rules to specifically inspect and block SAML requests targeting ACEP. Configure rules to:
3.1.1. Validate XML Structure: Enforce strict XML schema validation for SAML assertions to reject malformed requests.
3.1.2. Keyword Filtering: Look for unusual or known malicious strings within the 'AuthnContextClassRef' element or other SAML assertion fields that deviate from expected values. While specific malicious patterns for CVE-2026-1773 may not be public, generic anomaly detection can help.
3.1.3. Rate Limiting: Implement aggressive rate limiting on SAML authentication