CVE-2026-90010 in Linux
Summary
by MITRE • 09/16/2026
In the Linux kernel, the following vulnerability has been resolved:
scsi: bsg: Cap io_uring sense copy to max_response_len
Completion copied scmd->sense_len to the user response buffer without honoring max_response_len. After a valid sense, the midlayer sets sense_len to the real length (up to SCSI_SENSE_BUFFERSIZE), so a smaller user buffer was overrun.
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Analysis
by VulDB Data Team • 09/16/2026
The Linux kernel contains a critical memory safety vulnerability within the block layer generic scsi command interface, specifically affecting the io_uring integration for bsg requests. This flaw arises from an improper boundary check during the data transfer phase of SCSI sense information retrieval. When an application submits a request via io_uring to retrieve error details or status codes using the bsg interface, the kernel is responsible for copying the resulting sense buffer back to user space. The technical root cause lies in the completion handler which blindly copies scmd->sense_len bytes into the provided user response buffer without verifying that this length does not exceed max_response_len. This oversight ignores the explicit size constraint defined by the caller or the underlying request structure, leading directly to a heap-based buffer overflow condition where data is written beyond the allocated limits of the destination buffer.
The operational impact of this vulnerability is severe, as it allows for potential out-of-bounds writes that can corrupt adjacent memory structures within the kernel address space. An attacker with local access who can trigger this specific code path through crafted io_uring requests may achieve arbitrary code execution by overwriting critical function pointers or control data in nearby kernel objects. Even if full exploitation is not immediately feasible, the vulnerability compromises system stability and integrity, potentially leading to denial of service conditions due to memory corruption errors such as page faults or kernel panics. The severity is heightened because io_uring provides a high-performance interface that may be exposed to unprivileged users depending on system configuration, thereby expanding the attack surface significantly compared to traditional blocking syscalls.
From a classification perspective, this vulnerability aligns with CWE-120 Buffer Copy without Checking Size of Input Classic buffer overflow and specifically manifests as an out-of-bounds write which falls under CWE-787 Out-of-bounds Write in the Common Weakness Enumeration framework. In terms of tactical behavior within the MITRE ATT&CK for Enterprise or ICS frameworks, this flaw facilitates privilege escalation techniques where a low-privileged process escalates to kernel-level privileges by exploiting memory corruption during system call processing. The specific mechanism involves manipulating input parameters to bypass size validation checks before performing sensitive memory operations, which is characteristic of exploitation patterns targeting asynchronous I/O subsystems that handle variable-length data transfers without rigorous bounds checking.
Mitigation strategies require immediate patching of the affected Linux kernel versions to enforce strict length verification during sense buffer copying. Developers must ensure that any copy operation involving user-supplied buffers validates the source length against the destination capacity before execution, typically by using safe memory functions like memcpy_s or explicit conditional checks such as min(sense_len, max_response_len). System administrators should apply vendor-provided kernel updates promptly and restrict io_uring access to trusted users where possible. Additionally, enabling Kernel Self-Protection features such as KASAN can help detect similar out-of-bounds accesses during testing phases, while runtime protections like SMEP and SMAP provide additional layers of defense against exploitation attempts by preventing user-space code execution in kernel mode even if memory corruption occurs.