CVE-2026-90267 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
scsi: sd: Fix special_vec mempool leak when scsi_alloc_sgtables() fails
sd_set_special_bvec() allocates a special payload page for UNMAP and WRITE SAME commands. If scsi_alloc_sgtables() fails afterward in sd_setup_unmap_cmnd() or sd_setup_write_same{10,16}_cmnd(), the SCSI
midlayer does not call uninit_command() because RQF_DONTPREP is not set yet, leaking the page.
Call sd_uninit_command() on error, and clear RQF_SPECIAL_PAYLOAD after freeing the page.
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Analysis
by VulDB Data Team • 09/17/2026
The Linux kernel contains a resource management flaw within the SCSI disk driver subsystem that results in memory leaks during command setup failures. Specifically, this vulnerability affects the handling of special payload pages allocated for UNMAP and WRITE SAME commands. These operations are critical for storage efficiency but require specific internal structures to function correctly. The core issue arises from an inconsistency in error handling paths when allocating scatter-gather tables fails after a special vector has already been prepared by sd_set_special_bvec().
When the kernel prepares these SCSI commands, it first allocates and initializes a special payload page via sd_set_special_bvec(). This allocation is necessary to handle the specific data structures required for UNMAP and WRITE SAME operations. Subsequently, the driver attempts to allocate scatter-gather tables using scsi_alloc_sgtables() within functions such as sd_setup_unmap_cmnd() or sd_setup_write_same{10,16}_cmnd(). If this allocation fails due to memory pressure or other resource constraints, the error handling logic previously failed to properly clean up resources. The root cause is that the request flag RQF_DONTPREP was not yet set at the point of failure, which prevented the SCSI midlayer from invoking uninit_command() during its standard cleanup routine. Consequently, the special payload page allocated earlier remained in memory without being freed, leading to a persistent leak each time such an allocation error occurred.
This vulnerability is classified under CWE-401, which describes a missing release of memory after effective usage. In terms of operational impact, repeated occurrences of this flaw can lead to gradual kernel memory exhaustion over time. While individual leaks may seem negligible, they accumulate during high-load scenarios or when storage operations frequently encounter resource limitations. This progressive degradation of available system memory can eventually trigger the Linux Out-Of-Memory killer, potentially resulting in the termination of critical processes and service disruptions. Furthermore, such memory leaks contribute to increased kernel footprint, reducing overall system stability and performance efficiency on affected systems.
The remediation for this issue involves modifying the error handling path within the SCSI disk driver code. The fix ensures that sd_uninit_command() is explicitly called when scsi_alloc_sgtables() fails, thereby guaranteeing proper cleanup of allocated resources. Additionally, the patch mandates clearing the RQF_SPECIAL_PAYLOAD flag after freeing the page to maintain consistent state management and prevent double-free errors or invalid memory access in subsequent operations. This correction aligns with robust resource management practices expected in kernel development.
From a threat modeling perspective, this vulnerability does not directly enable remote code execution but represents an availability risk through denial of service via resource exhaustion. It maps to the ATT&CK technique T1496, which involves Resource Hijacking where attackers might exploit such leaks to degrade system performance or trigger crashes as part of a broader attack strategy aimed at disrupting services. Security practitioners should ensure that systems are updated with patches addressing this specific SCSI driver flaw. Regular monitoring for memory usage anomalies in kernel space can also help detect potential exploitation attempts or accidental triggers of the leak condition before significant impact occurs.