CVE-2026-99004 in Linux
Summary
by MITRE • 10/23/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/imagination: Size page table preallocation by device address
Commit 0a8224058a58 ("drm/imagination: Fix page count for page table for map() interface") passed the device address to pvr_mmu_op_context_create(), but the preallocation is still sized from device_addr + sgt_offset with an exclusive end. The offset into the object's pages has no place in a device-virtual range, and the exclusive end allocates one table too many when the range ends on a table boundary.
Count the tables from device_addr and the inclusive end of the range.
The new calculation does not take page table indices into account. This fixes another issue with the previous implementation, where the difference between start and end indices could underflow when a mapping crossed a page table boundary. This would lead to the driver preallocating a huge number of MMU pages, exhausting system memory and triggering an out of memory panic.
[Alessio: add paragraph to point out OOM bug being fixed, cc stable]
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Analysis
by VulDB Data Team • 10/24/2026
The vulnerability identified in the Linux kernel's DRM Imagination subsystem stems from an incorrect calculation logic used during page table preallocation for device address mappings. Specifically, within the pvr_mmu_op_context_create function, the system was sizing the preallocated memory based on a combination of the device address and a scatter-gather list offset with an exclusive end boundary. This approach is fundamentally flawed because offsets into object pages do not have semantic meaning in the context of device-virtual ranges. The use of an exclusive end value results in allocating one additional page table entry when the mapping range concludes exactly on a table boundary, leading to unnecessary resource consumption and potential instability even before more severe issues arise.
A critical consequence of this implementation flaw is a significant integer underflow vulnerability that occurs during memory management operations. When a virtual address mapping crosses a page table boundary, the calculation determining the difference between start and end indices can result in an unsigned integer underflow. This mathematical error causes the driver to interpret the required number of MMU pages as an extremely large value rather than the correct small count. Consequently, the kernel attempts to preallocate a massive amount of memory for these non-existent page tables, which rapidly exhausts available system resources and triggers an out-of-memory panic, effectively causing a denial of service condition for the entire system or specific processes relying on this graphics driver functionality.
From a classification perspective, this issue aligns with CWE-190 Integer Overflow or Wraparound due to the underflow in index calculation, as well as CWE-400 Resource Exhaustion resulting from the excessive memory allocation triggered by that error. In terms of attack vectors and tactical behavior within the MITRE ATT&CK framework, while often exploited indirectly through resource exhaustion techniques similar to T1498 Network Denial of Service or local privilege escalation via DoS if combined with other factors, the core technical flaw is a logic error in memory accounting (CWE-20 Improper Input Validation) that leads to uncontrolled resource consumption. The vulnerability primarily affects system stability and availability rather than directly compromising confidentiality or integrity through code execution, although an attacker could potentially leverage this for local denial of service attacks by triggering specific mapping patterns across page table boundaries.
The resolution involves correcting the preallocation logic to count tables based strictly on the device address and using an inclusive end boundary for the range calculation. This adjustment ensures that memory allocation matches the actual requirements without over-allocating or underflowing indices during cross-boundary mappings. To mitigate this risk, systems running affected kernel versions should apply the provided patch which corrects the arithmetic logic in the Imagination DRM driver. Additionally, administrators should ensure their kernels are updated to include stable fixes for this issue, as indicated by the inclusion of cc stable tags in the commit history, thereby preventing potential system crashes caused by memory exhaustion during graphics-intensive operations or complex virtual address mappings.