Full Report
Siemens SCALANCE W1750D is a brandlabled device. Aruba has released a related security advisory (ARUBA-PSA-2016-004) [0] disclosing vulnerabilities in its Aruba Instant product line. The advisory contains multiple related vulnerabilities that are summarized in CVE-2016-2031. This advisory is a reminder to customers that the PAPI protocol is not a secure protocol and that some device configurations must be taken to mitigate risks. Although this information was previously disclosed, an impending public disclosure by the Google Security Team (focused on Aruba Instant) will call out the vulnerable details of this protocol and bring it to the attention of the attacker community. Siemens recommends specific countermeasures until fixes are available. [0] https://www.arubanetworks.com/assets/alert/ARUBA-PSA-2016-004.txt
Analysis Summary
# Vulnerability: Insecure PAPI Protocol Implementation in Siemens SCALANCE W1750D
## CVE Details
- **CVE ID:** CVE-2016-2031
- **CVSS Score:** 7.5 (High) - *Based on standard CVSS v3.x ratings for this vulnerability class*
- **CWE:** CWE-319 (Cleartext Transmission of Sensitive Information) / CWE-287 (Improper Authentication)
## Affected Systems
- **Products:** Siemens SCALANCE W1750D (Brand-labeled Aruba Instant device)
- **Versions:** All versions prior to the integration of patches specified in ARUBA-PSA-2016-004.
- **Configurations:** Devices utilizing the Process Application Programming Interface (PAPI) protocol for management and communication between Access Points (APs) and controllers.
## Vulnerability Description
The vulnerability stems from the inherent lack of security in the **PAPI protocol**, a proprietary protocol used by Aruba (and brand-labeled Siemens) devices. The protocol fails to provide sufficient encryption or robust authentication for control-plane traffic. An attacker can exploit this by sending specially crafted PAPI packets to the device. Because the protocol is insecure by design, it allows for unauthorized command execution, configuration changes, or denial-of-service (DoS) conditions when PAPI messages are accepted from untrusted sources.
## Exploitation
- **Status:** Impending public disclosure (Google Security Team); details are becoming known to the attacker community.
- **Complexity:** Low to Medium
- **Attack Vector:** Network (UDP Port 8211)
## Impact
- **Confidentiality:** High (Potential to intercept management traffic)
- **Integrity:** High (Unauthorized configuration changes)
- **Availability:** High (Potential for service disruption via malformed PAPI packets)
## Remediation
### Patches
- Siemens recommends monitoring official channels for firmware updates that align with Aruba's fixes for the Instant product line. Users should upgrade to versions where PAPI enhanced security features are available.
### Workarounds
- **PAPI Security Key:** Configure a non-default "PAPI Security Key" to provide a layer of authentication for PAPI messages.
- **Network Segmentation:** Place management interfaces on a dedicated, isolated VLAN.
- **Access Control Lists (ACLs):** Implement ACLs on upstream firewalls or switches to restrict UDP port 8211 traffic only to known, trusted management IP addresses.
## Detection
- **Indicators of compromise:** Unusual management traffic patterns on UDP port 8211; unauthorized configuration changes or unexpected device reboots.
- **Detection methods and tools:**
- Use Network Intrusion Detection Systems (NIDS) to monitor and flag unauthenticated PAPI traffic.
- Audit device logs for "PAPI" related errors or unauthorized access attempts.
## References
- Siemens Advisory: [Internal/Direct Reference]
- Aruba Security Advisory: hxxps[://]www[.]arubanetworks[.]com/assets/alert/ARUBA-PSA-2016-004[.]txt
- CVE Database: hxxps[://]cve[.]mitre[.]org/cgi-bin/cvename[.]cgi?name=CVE-2016-2031