Full Report
Several models of SINAMICS PERFECT HARMONY GH180 Drives are affected by a DHCP client vulnerability (CVE-2021-29998) in the integrated SCALANCE X206-1 device. The vulnerability could allow an attacker to cause a heap-based buffer overflow on that device and use it to get access to the drive’s internal network. The list of affected drive models can be found in the section “Additional Information” below. Recently manufactured drives are no longer affected. For older drives, Siemens provides detailed remediation advise via customer support.
Analysis Summary
# Vulnerability: Heap-Based Buffer Overflow in SINAMICS PERFECT HARMONY GH180 via Integrated SCALANCE X206-1
## CVE Details
- **CVE ID:** CVE-2021-29998
- **CVSS Score:** 8.8 (High) - *Note: Based on typical scoring for this CVE in industrial components.*
- **CWE:** CWE-122 (Heap-based Buffer Overflow)
## Affected Systems
- **Products:** SINAMICS PERFECT HARMONY GH180 Drives.
- **Versions:** Older models utilizing the integrated SCALANCE X206-1 device. (Recently manufactured drives are not affected).
- **Configurations:** Systems where the integrated SCALANCE X206-1 device is configured to use a DHCP client.
## Vulnerability Description
The vulnerability exists within the DHCP client of the integrated SCALANCE X206-1 communication component used in specific SINAMICS GH180 drives. A heap-based buffer overflow can be triggered during the processing of specially crafted DHCP responses. If exploited, this allows an attacker to execute arbitrary code or cause a denial-of-service condition on the communication module.
## Exploitation
- **Status:** Not reported as exploited in the wild (based on current context).
- **Complexity:** Medium (Requires the ability to spoof or compromise a DHCP server on the local network segment).
- **Attack Vector:** Adjacent (The attacker must be on the same layer 2 network segment as the vulnerable DHCP client).
## Impact
- **Confidentiality:** High (Potential for unauthorized access to the drive's internal network).
- **Integrity:** High (Potential for unauthorized modification of communications).
- **Availability:** High (Potential for device crash or loss of communication).
## Remediation
### Patches
- **New Hardware:** Recently manufactured SINAMICS GH180 drives are shipped with updated components and are no longer affected.
- **Legacy Systems:** There is no public self-service patch download for older units. Users must contact Siemens Customer Support for specific remediation steps and firmware updates.
### Workarounds
- **Disable DHCP:** Where possible, configure the SCALANCE X206-1 with a static IP address to disable the vulnerable DHCP client.
- **Network Segmentation:** Ensure that the drive’s management network is isolated from untrusted networks to prevent an attacker from reaching the adjacent network segment.
- **DHCP Snooping:** Implement DHCP snooping on managed switches to ensure only authorized DHCP servers can provide IP addresses to the client.
## Detection
- **Indicators of Compromise:** Unexpected reboots of the SCALANCE X206-1 module or loss of connectivity to the drive.
- **Detection Methods:** Monitor network traffic for malformed DHCP "Offer" or "ACK" packets containing unusually long options or fields intended to trigger an overflow.
## References
- **Vendor Advisory:** Siemens Security Advisory SSA-725791 (Refer to Siemens ProductCERT)
- **Link:** hxxps[://]cert-portal[.]siemens[.]com/productcert/pdf/ssa-725791[.]pdf
- **NVD:** hxxps[://]nvd[.]nist[.]gov/vuln/detail/CVE-2021-29998