Full Report
Gridscale X Prepay contains multiple vulnerabilities that could allow an attacker to enumerate valid user names and to bypass locked-out user sessions. Siemens has released a new version for Gridscale X Prepay and recommends to update to the latest version.
Analysis Summary
# Vulnerability: User Enumeration and Session Bypass in Gridscale X Prepay
## CVE Details
- CVE ID: CVE-2025-40806, CVE-2025-40807
- CVSS Score: 6.3 (V3.1) / 6.9 (V4.0) (Highest referenced score is 6.9) (Medium/High)
- CWE: CWE-204 (Observable Response Discrepancy), CWE-294 (Authentication Bypass by Capture-replay)
## Affected Systems
- Products: Gridscale X Prepay
- Versions: All versions < V4.2.1
- Configurations: Not specified beyond the product/version context.
## Vulnerability Description
The advisory details two distinct vulnerabilities:
1. **CVE-2025-40806 (User Enumeration):** The affected application exhibits distinguishable responses based on whether a username is valid or invalid. This allows an unauthenticated remote attacker to enumerate valid user names, which facilitates subsequent brute-force attacks targeting known valid accounts. (CWE-204)
2. **CVE-2025-40807 (Session Bypass):** The application is vulnerable to the capture and replay of authentication tokens. This flaw allows an attacker who is authenticated but has subsequently been locked out of their session to re-establish a still-valid user session. (CWE-294)
## Exploitation
- Status: Not explicitly stated as exploited in the wild, but PoC potential is high given the nature of the flaws (username enumeration and replay attacks).
- Complexity: Low to Medium (User enumeration is often low complexity; replay attacks require prior authentication/session context).
- Attack Vector: Network (Both vulnerabilities are remotely exploitable over the network).
## Impact
| Metric | Impact Level |
| :--- | :--- |
| Confidentiality | Low (CVE-2025-40806: User list exposure aids further attacks; CVE-2025-40807: Access to existing session data) |
| Integrity | Low (CVE-2025-40807: Potential to maintain unauthorized access) |
| Availability | Low (CVE-2025-40807: Session bypass indirectly impacts availability management) |
*Note: Impact levels are inferred broadly from the vulnerability descriptions (enumeration and session maintenance).*
## Remediation
### Patches
Siemens has released a new version. Users should update to **Gridscale X Prepay Version V4.2.1 or newer**.
### Workarounds
The general security recommendations provided by Siemens should be followed:
1. Protect network access using appropriate mechanisms (e.g., firewalls, segmentation, VPN).
2. Configure the environment according to operational guidelines to run devices in a protected IT environment.
3. For critical power systems, ensure multi-level redundant secondary protection schemes are in place as required by regulations.
## Detection
- **Indicators of Compromise:** Monitoring for an unusually high rate of login attempts using various usernames (indicative of enumeration/brute force) or unusual persistence of user sessions post expected timeouts/lockouts.
- **Detection Methods and Tools:** Monitoring application logs for response discrepancies on login attempts and analyzing authentication token lifecycle events.
## References
- Siemens Security Advisory SSA-356310
- Vendor advisories page: hxxps://www.siemens.com/cert/advisories
- Terms of Use: hxxps://www.siemens.com/productcert/terms-of-use