CVE-2026-48741 in libiec61850
Summary
by MITRE • 10/16/2026
libIEC61850 is an open-source implementation of IEC 61850 client and server protocols including MMS, GOOSE, Sampled Values, and R-Session. Prior to 1.6.2, alternateArrayAccess in src/mms/iso_mms/server/mms_read_service.c does not validate an alternate-access sub-array range when numberOfElements is greater than zero. An out-of-range MmsValue_getElement call returns NULL, and the sub-array branch passes that value to MmsValue_isDeletable, causing a NULL pointer dereference. A remote MMS Read request can therefore crash servers whose data models contain arrays, while the single-element error path handles the same invalid index safely. This issue is fixed in version 1.6.2.
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Analysis
by VulDB Data Team • 10/16/2026
The libIEC61850 library serves as a critical open-source implementation of the IEC 61850 protocol suite, which underpins modern smart grid automation and control systems. It facilitates communication between intelligent electronic devices by supporting key protocols such as Manufacturing Message Specification (MMS), Generic Object Oriented Substation Event (GOOSE), Sampled Values, and R-Session. Within this ecosystem, the MMS Read service is a fundamental mechanism allowing clients to retrieve data from servers based on defined data models. These data models frequently utilize complex structures including arrays of values, which are essential for representing multi-point measurements or configuration parameters in industrial control environments. The integrity of array access operations within these protocols is paramount, as any failure can disrupt the reliability and availability of critical infrastructure monitoring and control functions.
A significant vulnerability exists in versions of libIEC61850 prior to 1.6.2, specifically located in the alternateArrayAccess function within the source file src/mms/iso_mms/server/mms_read_service.c. The technical flaw stems from an insufficient validation of array bounds when handling sub-arrays where the numberOfElements parameter is greater than zero. When a remote MMS Read request targets such a structure with an invalid index, the underlying call to MmsValue_getElement fails to return a valid pointer and instead yields NULL. However, the subsequent code path does not adequately check for this null condition before proceeding. Instead of handling the error gracefully as it does in single-element access scenarios, the logic passes the NULL value directly into the MmsValue_isDeletable function. This sequence results in a classic NULL pointer dereference, causing an immediate crash or segmentation fault within the server process.
The operational impact of this vulnerability is severe for organizations relying on IEC 61850 compliant systems. Because the flaw can be triggered by a remote MMS Read request, it presents a Remote Code Execution risk in terms of availability rather than confidentiality or integrity initially. An unauthenticated attacker could exploit this condition to cause a Denial of Service against critical control servers that manage arrays within their data models. In industrial settings where continuous monitoring is required, such crashes can lead to blind spots in system visibility and potential instability if the server fails to restart automatically or recover state correctly. The inconsistency between how single-element errors are handled safely versus array sub-elements highlights a gap in defensive programming practices regarding complex data structures.
This vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-476, which describes NULL Pointer Dereference. It also relates to CWE-20, Improper Input Validation, as the root cause is the failure to validate that array indices fall within acceptable bounds before accessing memory. From a cyber kill chain perspective, this flaw can be leveraged via MITRE ATT&CK technique T1499, Endpoint Denial of Service, or potentially T1529 if used in conjunction with other actions to disrupt operations during an attack. The exploitation vector is network-based, making it accessible to any entity that can reach the MMS service port on the affected server.
To mitigate this risk, organizations must immediately upgrade libIEC61850 to version 1.6.2 or later, where the alternateArrayAccess function has been patched to properly validate sub-array ranges and handle NULL returns safely. For environments where immediate patching is not feasible due to operational constraints, network segmentation strategies should be employed to restrict access to MMS ports exclusively to trusted management networks. Additionally, implementing intrusion detection systems that monitor for anomalous MMS traffic patterns can provide an additional layer of defense against exploitation attempts while the underlying software vulnerability remains unpatched in legacy systems.