ABB AC500 V3 Firmware Fixes Web Visualization Denial of Service
Tech GuruQuick Answer
The authority published 3ADR011565 for ABB AC500 V3 PLC firmware before 3.9.1 when the web server is enabled. An update is available that resolves publicly reported vulnerability in the products versions listed as affected in the advisory. An attacker who successfully exploited these vulnerabilities could cause a denial-of-service (DoS). A vulnerability in the runtime system's CmpVisuServer component allows attackers to cause a denial-of-service (DoS) by sending special request to the web visualization. The issue is triggered by an internal read access using a pointer of wrong type. The vulnerability can only be exploited if the web server is running. Affected deployments should be matched to the authority's exact scope and moved to the supported fixed release.
Confirm Scope And Apply The Supported Fix
What to do now: Inventory ABB AC500 V3 PLC firmware before 3.9.1 when the web server is enabled, match the exact affected release or feature, apply the authority-supported fixed build or service remediation, validate the dependent workflow, and preserve evidence.
Last verified: 2026-09-28 UTC. Recheck the authoritative advisory and supported distribution channel before changing production.
Scope And Authority
| Product scope | ABB AC500 V3 PLC firmware before 3.9.1 when the web server is enabled |
|---|---|
| Advisory | 3ADR011565 |
| CVE | CVE-2025-41738 |
| Authoritative release date | 2026-09-28 00:30:00 UTC (ABB CSAF initial release); added to the ABB CSAF feed at 2026-09-28 12:10:00 UTC |
| Authority revision date | 2026-09-28 00:30:00.000 UTC |
| Affected versions | ABB AC500 V3 PLC firmware before 3.9.1 with the web visualization server enabled. |
| Fixed version | ABB AC500 V3 firmware 3.9.1, integrated into Automation Builder 2.9.1 |
| CVSS base score | 7.5 (CVSS v3.1) |
| CVSS severity | High |
| Exploitation status | Not stated by the authority; no exploitation claim is inferred. |
What Changed
An update is available that resolves publicly reported vulnerability in the products versions listed as affected in the advisory. An attacker who successfully exploited these vulnerabilities could cause a denial-of-service (DoS). A vulnerability in the runtime system's CmpVisuServer component allows attackers to cause a denial-of-service (DoS) by sending special request to the web visualization. The issue is triggered by an internal read access using a pointer of wrong type. The vulnerability can only be exploited if the web server is running.
What To Validate Now
- Inventory. Locate ABB AC500 V3 PLC firmware before 3.9.1 when the web server is enabled deployments, versions, enabled features, exposure paths, owners, and dependent services.
- Establish applicability. Compare each deployment with the authority's affected-version statement: ABB AC500 V3 PLC firmware before 3.9.1 with the web visualization server enabled. Do not infer applicability from product family or severity alone.
- Remediate. Apply ABB AC500 V3 firmware 3.9.1, integrated into Automation Builder 2.9.1 through the supported vendor or project channel, following the current advisory and change-control requirements.
- Validate. Confirm the resulting version or managed-service state, exercise representative functionality and recovery paths, monitor for regressions, and document exceptions.
- Retain evidence. Preserve asset and owner identifiers, the applicability decision, before-and-after versions, change approval, installation output, validation results, and any exception or rollback record.
Operational Cautions
Use the exact supported release stream and repository. Test dependencies, clusters, integrations, and rollback before broad deployment; a CVSS rating or reachable feature is not evidence of exploitation.
Evidence To Retain
- Exact product, release stream, package or application version, enabled feature, environment, and accountable owner.
- UTC timestamps, authority revision, approved change record, installer or package-manager output, and resulting version.
- Relevant logs and monitoring evidence, test results, exceptions, compensating controls, and rollback decisions.
Related TechGeeks Resources
Authoritative References
Correction policy: If the authority changes affected versions, fixed versions, severity, exploitation information, mitigations, or required action, TechGeeks will update this notice and its verification date.
