Siemens SIMATIC CP 1543-1 SNMP Write Privilege Bypass Vulnerability (CVE-2016-8562) Security Advisory
Executive & SecOps Summary
SECOPS ASSESSMENTSiemens SIMATIC CP 1543-1 and SIPLUS NET CP 1543-1 (All versions < V2.0.28)
Unauthorized modification of read-only SNMP variables via port 161/udp, potentially leading to reduced availability or Denial-of-Service (DoS)
Immediately upgrade firmware to V2.0.28 or higher, and restrict access to port 161/udp using network firewalls
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Siemens recommends upgrading the firmware of affected devices to V2.0.28 or later. Download the official firmware update from the Siemens Industry Online Support portal and verify its integrity before deployment.
# Verify the integrity of the downloaded Siemens firmware update file using SHA-256
echo 'expected_sha256_hash_here CP1543_V2_0_28.upd' | sha256sum --check2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, restrict network access to port 161/udp. Use firewalls to permit SNMP traffic only from authorized engineering workstations (e.g., 192.168.1.50).
# Block unauthorized SNMP traffic and allow only the trusted engineering workstation
iptables -A INPUT -p udp --dport 161 -s 192.168.1.50 -j ACCEPT
iptables -A INPUT -p udp --dport 161 -j DROP
# Save the iptables rules to persist across reboots
if [ -f /etc/iptables/rules.v4 ]; then
iptables-save > /etc/iptables/rules.v4
fi3. Log Audit & IoC Verification Commands
Scan your OT network to identify active SNMP services on Siemens communication processors using network auditing tools.
# Scan the target subnet to detect active SNMP services and retrieve system information
nmap -sU -p 161 --script snmp-info 192.168.1.0/24Stop Exposing VPN Ports to the Internet — Switch to Zero-Trust Access
Eliminate public-facing VPN concentrators and firewall management ports with identity-first Zero-Trust Network Access.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability exists in the Siemens SIMATIC CP 1543-1 and SIPLUS NET CP 1543-1 communications processors. The root cause is an improper access control implementation where SNMP variables, which are designed to be read-only and configurable solely via the TIA-Portal, can be modified under specific conditions via port 161/udp.
2. Exploitation Mechanics & Attack Scenario
An attacker with network access to port 161/udp of the target device can transmit crafted SNMP Set requests. Because the device fails to properly enforce read-only restrictions on these specific system variables, the unauthorized write operations are processed. This allows the attacker to alter critical system parameters, leading to device instability.
3. Infrastructure & Business Impact
These communication processors are critical components in Industrial Control Systems (ICS) and Operational Technology (OT) environments, bridging PLCs and upper-level networks. Exploitation of this vulnerability to cause a Denial-of-Service (DoS) can disrupt real-time industrial processes, halt production lines, and impact overall operational safety.
Official Vendor Advisories & References
A vulnerability has been identified in SIMATIC CP 1543-1 (All versions < V2.0.28), SIPLUS NET CP 1543-1 (All versions < V2.0.28). Under special conditions it was possible to write SNMP variables on port 161/udp which should be read-only and should only be configured with TIA-Portal. A write to these variables could reduce the availability or cause a denial-of-service.
Frequently Asked SecOps Questions (CVE-2016-8562)
FAQQ1. How critical is CVE-2016-8562 and is it actively exploited in the wild?
CVE-2016-8562 is rated CVSS 7.5 (HIGH) with a 30-day EPSS exploitation probability of 3.6%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2016-8562?
Primary impacted vendors include siemens across simatic cp 1543-1, siplus net cp 1543-1. Scope summary: SIMATIC CP 1543-1 (All versions < V2.0.28), SIPLUS NET CP 1543-1 (All versions < V2.0.28)
Q3. What temporary mitigations or workarounds exist for CVE-2016-8562 before patching?
[Mitigation] Immediately upgrade firmware to V2.0.28 or higher, and restrict access to port 161/udp using network firewalls Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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