CVE-2026-78012 Overview
CVE-2026-78012 is a stack-based buffer overflow [CWE-121] in the NetStaX EtherNet/IP Stack from Pyramid Solutions. Versions prior to v5.6.1 fail to validate the size of incoming Class 3 explicit-message requests against the application-side receive buffer. An attacker on the network can send an oversized Class 3 explicit message to a vulnerable industrial device. The receiving stack copies the request into an undersized buffer without generating a Common Industrial Protocol (CIP) error. The overflow can cause memory corruption, a device crash, or provide a remote code execution vector.
Critical Impact
Unauthenticated network attackers can silently overflow receive buffers in industrial control devices, potentially achieving remote code execution or denial of service without triggering CIP error responses.
Affected Products
- Pyramid Solutions NetStaX EtherNet/IP Stack prior to v5.6.1
- Industrial devices integrating the NetStaX EtherNet/IP protocol stack
- CIP-enabled products relying on NetStaX for Class 3 explicit messaging
Discovery Timeline
- 2026-09-01 - CVE-2026-78012 published to the National Vulnerability Database
- 2026-09-01 - Last updated in NVD database
Technical Details for CVE-2026-78012
Vulnerability Analysis
The vulnerability resides in how the NetStaX EtherNet/IP Stack handles Class 3 explicit-message requests. Class 3 messaging is a connected messaging service in the CIP protocol used for non-time-critical data exchange between industrial devices. The stack accepts these requests over TCP on the standard EtherNet/IP port 44818.
When a request arrives, the stack copies the payload into an application-side receive buffer. The implementation does not verify that the incoming payload length fits within the destination buffer. An oversized request writes past the buffer boundary and corrupts adjacent stack memory.
The silent nature of the flaw amplifies its impact. The originating device receives no CIP error indicating that the request could not be processed. Operators lose visibility into malformed traffic while the target device experiences memory corruption or crashes.
Root Cause
The root cause is missing bounds checking on the length field of Class 3 explicit-message requests before a memory copy into the receive buffer. This is a classic stack-based buffer overflow condition classified under [CWE-121].
Attack Vector
The attack requires only network reachability to the vulnerable device. No authentication or user interaction is needed. An attacker crafts a Class 3 explicit-message request with a payload larger than the receive buffer and sends it to the target. The stack copies the payload without validation, corrupting memory. Depending on memory layout and platform architecture, outcomes range from a device crash to arbitrary code execution on the industrial controller.
Refer to the Pyramid Solutions Vulnerability Advisory for protocol-level details.
Detection Methods for CVE-2026-78012
Indicators of Compromise
- Unexplained crashes, watchdog resets, or reboots on EtherNet/IP-enabled industrial devices
- Class 3 explicit-message requests with payload lengths exceeding standard CIP message sizes
- Loss of communication with programmable logic controllers (PLCs) or CIP endpoints following inbound traffic on TCP port 44818
- CIP sessions that terminate without a corresponding CIP error response to the originator
Detection Strategies
- Deploy deep packet inspection on OT network segments to parse EtherNet/IP traffic and flag Class 3 explicit messages exceeding expected size thresholds
- Correlate device availability events with inbound EtherNet/IP traffic patterns to identify crash-inducing packets
- Baseline normal CIP explicit-message sizes per device and alert on outliers
Monitoring Recommendations
- Monitor TCP port 44818 and UDP port 2222 for anomalous packet sizes and connection patterns
- Log all EtherNet/IP session terminations and correlate against device health telemetry from the ICS environment
- Forward OT network telemetry into a centralized data lake for cross-referencing with endpoint and identity events
How to Mitigate CVE-2026-78012
Immediate Actions Required
- Upgrade the NetStaX EtherNet/IP Stack to v5.6.1 or later on all affected devices
- Contact device vendors that embed the NetStaX stack to obtain updated firmware
- Restrict network access to EtherNet/IP devices using firewall rules that permit CIP traffic only from authorized engineering workstations and controllers
- Segment OT networks from IT networks and the internet following IEC 62443 zone-and-conduit guidance
Patch Information
Pyramid Solutions released NetStaX v5.6.1 to address the missing bounds check on Class 3 explicit-message requests. Details on the fix are available in the Pyramid Solutions Vulnerability Advisory. Operators should coordinate patch deployment with device manufacturers, since many industrial products bundle the stack in signed firmware.
Workarounds
- Block inbound TCP port 44818 at network boundaries where CIP messaging is not required
- Enforce allowlists of source IP addresses permitted to initiate Class 3 explicit-message sessions with each device
- Deploy an industrial firewall or CIP-aware intrusion prevention system to drop malformed or oversized explicit-message requests
- Disable Class 3 explicit messaging on devices where the feature is not operationally required
# Example iptables rule to restrict EtherNet/IP traffic to authorized engineering workstation
iptables -A INPUT -p tcp --dport 44818 -s 10.10.20.15 -j ACCEPT
iptables -A INPUT -p tcp --dport 44818 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.