CVE-2026-68340 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
hwmon: occ: validate poll response sensor blocks
The OCC poll response parser walks a counted list of sensor data blocks. It used the static backing-array capacity as the parse boundary, but a transport response makes only data_length bytes current and valid. A truncated response can therefore make the parser consume a block header or block extent outside the current response.
Use data_length as the parent boundary, prove the fixed poll header and each current block header before reading them, and prove the complete block before advancing. Keep parsed sensor metadata local until the complete response has passed validation, then publish it. Propagate malformed-response errors before publishing the OCC as active.
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability in question affects the Linux kernel's hardware monitoring subsystem, specifically within the OCC (Open Compute Platform) driver implementation. This issue resides in the hwmon subsystem which is responsible for monitoring hardware components such as temperature, voltage, and fan speeds. The OCC driver interface is commonly used in data center environments to communicate with hardware monitoring controllers that provide sensor data from system components. When processing poll responses from these hardware controllers, the kernel's parsing logic fails to properly validate response boundaries, creating a potential for out-of-bounds memory access. This type of vulnerability falls under the CWE-129 weakness category which deals with insufficient validation of length of input buffers, and represents a classic buffer over-read scenario that could be exploited to gain unauthorized access to system memory or cause denial of service conditions.
The technical flaw manifests in how the OCC poll response parser processes sensor data blocks. The parser operates on a counted list of sensor data blocks but incorrectly uses the static backing array capacity as its boundary condition instead of the actual data_length field from the transport response. This discrepancy allows an attacker to craft a truncated response that causes the parser to access memory locations beyond the valid response boundaries, potentially reading uninitialized memory or data from adjacent memory regions. The parser processes block headers and extents without proper validation of the response structure, meaning it reads header information before confirming that the entire block structure is present and valid within the response bounds. This violates fundamental security principles of input validation and boundary checking that are essential for preventing memory corruption vulnerabilities.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to potentially enable more sophisticated attacks. An attacker who can control or influence network traffic to the OCC monitoring interface could exploit this flaw to read sensitive kernel memory contents, potentially extracting system information, credentials, or other confidential data. The vulnerability affects systems that rely on OCC interfaces for hardware monitoring in data center environments, particularly those using IBM Power Systems or similar platforms that implement Open Compute Platform specifications. The risk is elevated in multi-tenant environments where an attacker might be able to send malformed responses through shared network paths or by compromising systems within the same network segment. This vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter and T1566.002 for phishing via social engineering, as it could potentially enable initial access or privilege escalation in environments where hardware monitoring interfaces are exposed.
The fix implemented addresses this vulnerability by introducing proper boundary validation throughout the parsing process. Instead of using static array capacity as the parse limit, the solution employs data_length as the primary boundary condition for all response processing. Each poll header and block header is validated before any data is read from it, ensuring that the parser only accesses memory locations that are actually part of the current transport response. The implementation also includes comprehensive validation of entire blocks before advancing to the next parsing step, preventing partial or corrupted blocks from being processed. Sensor metadata is kept local until complete response validation is achieved, and only then is it published to the system for use by other components. Malformed-response errors are propagated upstream before the OCC interface is activated, ensuring that invalid responses are rejected at the earliest possible point in the processing chain. This approach follows security best practices outlined in the CERT/CC secure coding guidelines and aligns with defensive programming principles that emphasize input validation and proper boundary checking to prevent memory corruption vulnerabilities.