Overview
In the ever-evolving world of cybersecurity, vulnerabilities are constantly being discovered and patched. One such vulnerability, identified as CVE-2025-40566, has been found in Siemens’ SIMATIC PCS neo V4.1 and SIMATIC PCS neo V5.0 products. The severity of this vulnerability, coupled with its potential to compromise systems and leak sensitive data, has put the cybersecurity community on high alert. This blog post aims to provide an in-depth understanding of the vulnerability, its potential impact, and how to mitigate it effectively.
Vulnerability Summary
CVE ID: CVE-2025-40566
Severity: High (8.8 CVSS score)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: System compromise and data leakage
Affected Products
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Product | Affected Versions
SIMATIC PCS neo V4.1 | All versions < V4.1 Update 3 SIMATIC PCS neo V5.0 | All versions < V5.0 Update 1 How the Exploit Works
The vulnerability lies in the improper invalidation of user sessions upon logout. In a secure system, a user’s session should be invalidated or destroyed as soon as they log out. However, in the affected versions of SIMATIC PCS neo, the user’s session remains active even after logout. This means that an attacker who has somehow obtained the session token can re-use a legitimate user’s session. This vulnerability could be exploited by a remote unauthenticated attacker, leading to potential system compromise or data leakage.
Conceptual Example Code
Here is a conceptual example of how an attacker might exploit this vulnerability. An attacker could intercept a valid session token and use it to send a malicious request to a vulnerable endpoint:
GET /sensitive/data HTTP/1.1
Host: target.example.com
Cookie: sessionid=valid_session_token_obtained_by_attackerIn this example, the attacker uses the valid session token to send a GET request to a sensitive data endpoint. Since the session token is still valid, even after the legitimate user has logged out, the attacker can gain unauthorized access to the sensitive data.
Mitigation
Users of affected versions of SIMATIC PCS neo are advised to apply the vendor-provided patch immediately. The patch ensures that user sessions are invalidated upon logout, thus closing the vulnerability. For those unable to apply the patch immediately, a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can provide temporary mitigation. These systems can monitor and block suspicious activities, such as the re-use of session tokens. Nonetheless, these are only temporary solutions and applying the vendor patch is the most effective way to secure the system against this vulnerability.