CVE-2026-111732 in P-Net
Summary
by MITRE • 10/29/2026
P-Net before 1.0.3, when built with PNET_OPTION_AR_VENDOR_BLOCKS enabled, parses a data length from a field of the ARVendorBlock request that is not part of the block definition and uses it as the number of bytes to copy into a fixed-size buffer, without comparing it with the buffer size or the block length. A crafted Connect request causes an out-of-bounds write. This can lead to a crash (denial of service) or potentially arbitrary code execution.
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Analysis
by VulDB Data Team • 10/29/2026
The vulnerability identified in P-Net versions prior to 1.0.3 represents a critical memory safety flaw rooted in improper input validation and buffer management within the ARVendorBlock parsing logic. Specifically, when the software is compiled with the PNET_OPTION_AR_VENDOR_BLOCKS feature enabled, it processes incoming request data by extracting a length field from an ARVendorBlock structure. However, this extraction targets a byte offset that does not correspond to any defined member of the block's formal specification. Instead of relying on validated structural boundaries or explicit size indicators provided by the protocol standard, the application blindly interprets arbitrary bytes as a copy count and proceeds to write that quantity of data into a fixed-size buffer allocated for handling vendor-specific information. This fundamental design error bypasses essential bounds checking mechanisms, allowing an attacker who can inject crafted network traffic to dictate exactly how much memory is overwritten beyond the intended allocation limits.
From a technical perspective, this flaw constitutes a classic out-of-bounds write vulnerability, which falls under CWE-787 in the Common Weakness Enumeration taxonomy. The absence of validation against either the actual buffer size or the declared length of the vendor block creates a direct path for memory corruption. When a malicious actor sends a specially constructed Connect request containing an excessively large value in this specific field position, the application copies data past the end of the allocated heap or stack segment. This overflow can corrupt adjacent memory structures, including return addresses, function pointers, or other critical control flow metadata stored on the call stack or within linked list headers. Such corruption destabilizes the program's execution environment and provides a potential vector for achieving arbitrary code execution if an attacker can carefully craft the payload to overwrite executable instructions or security-critical data structures with shellcode or ROP gadgets.
The operational impact of this vulnerability is severe, ranging from service disruption to complete system compromise. In its most immediate manifestation, the out-of-bounds write triggers a segmentation fault or access violation, resulting in an application crash that denies service to legitimate users attempting to connect via P-Net protocols. This aligns with denial-of-service attack patterns documented under MITRE ATT&CK technique T1499, specifically endpoint process hijacking or resource exhaustion through crashes. However, the risk extends far beyond simple availability loss. If the underlying system architecture and compiler settings permit it, such as when stack canaries are disabled or ASLR is ineffective, an attacker could leverage this memory corruption to execute arbitrary commands with the privileges of the P-Net service process. This capability allows for lateral movement within industrial networks where P-Net is commonly deployed for fieldbus communication between PLCs and I/O devices.
It is crucial to note that this vulnerability requires specific configuration conditions to be exploitable, as the affected code path is gated by the compilation flag PNET_OPTION_AR_VENDOR_BLOCKS. By default, this option is disabled in standard builds of P-Net, meaning many deployments may not be immediately susceptible unless explicitly configured with vendor block support enabled for custom protocol extensions or debugging purposes. Despite this mitigation through configuration defaults, any organization that has intentionally enabled this feature must treat the vulnerability as high severity due to its potential for remote code execution over network interfaces exposed to untrusted zones.
To mitigate this risk, immediate action should focus on upgrading P-Net to version 1.0.3 or later, where the parsing logic has been corrected to validate buffer boundaries before performing memory copy operations. If an upgrade is not immediately feasible and the application must remain in a vulnerable state for legacy compatibility reasons, administrators should ensure that the PNET_OPTION_AR_VENDOR_BLOCKS flag remains disabled during compilation unless absolutely necessary for specific vendor integrations. Furthermore, network segmentation strategies should be employed to restrict access to P-Net services from untrusted networks, ensuring that only authorized industrial control system components can send Connect requests and other protocol messages. Implementing strict input validation at the gateway level or using intrusion detection systems capable of identifying anomalous packet structures in proprietary protocols can also provide an additional layer of defense against exploitation attempts targeting this memory corruption flaw.