CVE-2026-124758 in P-Net
Summary
by MITRE • 11/13/2026
P-Net before 1.0.4 does not check the record data length of an IODWrite request to a non-user record index against the size of the record block header. The 32-bit length is reduced by the header size before it is passed to the record handlers, so a length smaller than the header underflows and the handlers receive a data length of about 65530. The fixed-size reads of the I&M and PDPort handlers can then read past the end of the session buffer. The result of the write is discarded. The attacker must have an established Application Relationship or be able to send in the context of one, and requires ADJACENT network access.
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Analysis
by VulDB Data Team • 11/13/2026
The vulnerability identified in P-Net versions prior to 1.0.4 represents a critical integer underflow flaw within the processing logic for IODWrite requests targeting non-user record indices. This defect stems from an insufficient validation of input data lengths, specifically failing to verify that the provided record data length is adequate relative to the size of the associated record block header. In this specific implementation, the system performs arithmetic operations on a 32-bit integer representing the data length by subtracting the fixed size of the header before passing the result to subsequent record handlers. When an attacker supplies a length value that is smaller than the header size, the subtraction operation results in a signed-to-unsigned conversion error or simple underflow due to unsigned arithmetic wrapping around. Consequently, instead of receiving a small positive integer representing valid data payload, the handlers are passed a massive value approximately equal to 65530 bytes.
This erroneous length parameter directly facilitates an out-of-bounds read vulnerability within the I&M and PDPort record handlers. These components utilize fixed-size read operations that rely on the provided length to determine how much memory to access from the session buffer. Because the underflowed value is significantly larger than the actual available data in the buffer, these handlers proceed to read past the allocated boundaries of the session buffer. This behavior constitutes a classic out-of-bounds read condition, which can lead to information disclosure if the accessed memory contains sensitive data such as cryptographic keys or internal system states. Although the documentation notes that the result of this write operation is discarded and does not directly cause a crash or arbitrary code execution through memory corruption in this specific vector, the ability to leak kernel or application memory remains a severe security risk.
From an operational impact perspective, this vulnerability allows for potential side-channel attacks or information leakage against the P-Net stack. An attacker who successfully exploits this flaw can extract data from adjacent memory locations that were not intended to be accessible via the IODWrite interface. This compromises the confidentiality of the system's internal state and may provide footholds for further exploitation if combined with other vulnerabilities. The attack requires specific conditions, notably that the adversary must possess an established Application Relationship or have the capability to send packets within such a context. Furthermore, network access is restricted to adjacent networks, meaning remote attackers over the public internet cannot directly exploit this flaw without first compromising a host on the local segment or having physical proximity to the industrial control system network.
Mitigation strategies primarily involve upgrading P-Net to version 1.0.4 or later, where the developers have implemented proper bounds checking for record data lengths against header sizes before arithmetic operations are performed. For environments where immediate patching is not feasible, defense-in-depth measures should be employed. Network segmentation is critical; administrators should ensure that only trusted hosts with legitimate Application Relationships can communicate on the network segments hosting P-Net devices. Additionally, implementing strict access control lists and monitoring for anomalous packet sizes or unusual IODWrite request patterns can help detect attempted exploitation of this integer underflow vulnerability before it results in successful memory disclosure.
This vulnerability aligns with Common Weakness Enumeration (CWE) identifiers such as CWE-190 Integer Overflow or Wraparound, which describes the arithmetic error leading to the incorrect length value, and CWE-787 Out-of-bounds Read, which characterizes the resulting memory access violation. In terms of attack tactics, this scenario maps to MITRE ATT&CK techniques related to Collection via Network Sniffing or potentially T1056 Input Capture if the leaked data includes credentials, although the primary classification here is information leakage through improper input validation and boundary checks in industrial protocol implementations.