Full Report
SIMATIC S7 PLCs contain multiple vulnerabilities in the web server that could allow an attacker to perform cross-site scripting attacks. Siemens has released new versions for several affected products and recommends to update to the latest versions. Siemens is preparing further fix versions and recommends specific countermeasures for products where fixes are not, or not yet available.
Analysis Summary
# Vulnerability: Multiple Cross-Site Scripting (XSS) Vulnerabilities in SIMATIC S7 PLCs Web Server
## CVE Details
- **CVE ID:** CVE-2026-25786, CVE-2026-25787, CVE-2026-25789
- **CVSS Score:** 9.1 (Critical) [v3.1] / 9.3 (Critical) [v4.0]
- **CWE:** CWE-79 (Improper Neutralization of Input During Web Page Generation)
## Affected Systems
- **Products:**
- SIMATIC Drive Controller family (CPU 1504D TF, CPU 1507D TF)
- SIMATIC ET 200SP Open Controller (PC, PC2, and PC3 variants)
- SIMATIC S7-1500 CPU family (including related ET 200 CPUs and SIPLUS variants)
- **Versions:**
- Drive Controllers: All versions < V3.1.6
- ET 200SP Open Controllers: All versions (V2, V3, V4 CPUs)
- **Configurations:** Systems with the integrated Web Server functionality enabled.
## Vulnerability Description
Affected SIMATIC S7 PLCs contain multiple flaws in how the web server validates and sanitizes input before rendering it in the user's browser:
- **CVE-2026-25786:** Improper sanitization of the "Project Name" rendered on the CPU's "Home" page. An attacker authorized to download a TIA project can inject malicious scripts.
- **CVE-2026-25787:** Improper sanitization of "Technology Object (TO)" names on the "Motion Control Diagnostics" page.
- **CVE-2026-25789:** Improper validation of filenames on the "Firmware Update" page, allowing script execution via social engineering during the file selection process (even without a completed upload).
## Exploitation
- **Status:** Not exploited in the wild (reported via coordinated disclosure).
- **Complexity:** Low to Medium (CVE-2026-25789 requires high AC/social engineering).
- **Attack Vector:** Network.
## Impact
- **Confidentiality:** High (Session hijacking, credential theft).
- **Integrity:** High (Unauthorized execution of commands in the context of an authenticated user).
- **Availability:** High.
## Remediation
### Patches
Siemens has released the following updates to address these vulnerabilities:
- **SIMATIC Drive Controller CPU 1504D/1507D TF:** Update to V3.1.6 or later.
- **Other Products:** Fixes are currently being prepared; users should monitor the Siemens ProductCERT portal for updates.
### Workarounds
- **Deactivate the Web Server:** If not required for operation, disable the web server functionality in the device configuration.
- **Restrict Access:** Use firewalls and VLANs to limit access to the web server (TCP/80 and TCP/443) only to trusted administrative workstations.
- **Project Protection:** Use the TIA Portal’s "Protection" settings to restrict who can download projects to the PLC.
## Detection
- **Indicators of Compromise:** Review web server access logs for unusual requests or characters in fields associated with Project Names or Technology Objects.
- **Detection Methods:** Vulnerability scanners can identify outdated firmware versions; manual inspection of TIA Portal project metadata for embedded scripts.
## References
- Siemens Security Advisory SSA-688146: [https://cert-portal.siemens.com/productcert/pdf/ssa-688146.pdf](https://cert-portal.siemens.com/productcert/pdf/ssa-688146.pdf)
- Siemens ProductCERT: [https://www.siemens.com/cert/advisories](https://www.siemens.com/cert/advisories)
- Firmware Downloads: [https://support.industry.siemens.com/cs/ww/en/view/109773914/](https://support.industry.siemens.com/cs/ww/en/view/109773914/)