CVE-2026-43093 in Linux
Summary
by MITRE • 05/06/2026
In the Linux kernel, the following vulnerability has been resolved:
xsk: tighten UMEM headroom validation to account for tailroom and min frame
The current headroom validation in xdp_umem_reg() could leave us with insufficient space dedicated to even receive minimum-sized ethernet frame. Furthermore if multi-buffer would come to play then skb_shared_info stored at the end of XSK frame would be corrupted.
HW typically works with 128-aligned sizes so let us provide this value as bare minimum.
Multi-buffer setting is known later in the configuration process so besides accounting for 128 bytes, let us also take care of tailroom space upfront.
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Analysis
by VulDB Data Team • 06/24/2026
The vulnerability addressed in this linux kernel patch relates to the XDP (eXpress Data Path) user memory (UMEM) registration mechanism within the kernel's networking stack. This issue specifically affects the xsk (XDP Socket) subsystem which provides high-performance packet processing capabilities for network applications. The core problem lies in the insufficient validation of memory allocation parameters during UMEM registration, creating potential for packet corruption and system instability. The vulnerability stems from inadequate headroom calculation that fails to account for the complete memory requirements necessary for proper frame handling.
The technical flaw manifests in the xdp_umem_reg() function where the headroom validation logic does not properly consider both tailroom requirements and minimum frame sizes needed for ethernet packet processing. When the kernel allocates memory for XSK frames, it must ensure sufficient space not only for the packet data but also for the metadata structures that accompany each frame. The current implementation leaves insufficient headroom space, potentially causing the system to allocate memory that cannot accommodate even the smallest valid ethernet frames. This fundamental miscalculation becomes particularly problematic when multi-buffer configurations are employed, as the skb_shared_info structure stored at the end of XSK frames would become corrupted due to insufficient space allocation.
The operational impact of this vulnerability extends beyond simple memory allocation issues to potentially compromise network packet processing integrity. Network applications relying on XDP for high-speed packet handling could experience corrupted packet data, dropped packets, or even system crashes when the memory allocation constraints are violated. The vulnerability particularly affects systems utilizing hardware offloading capabilities that typically operate with 128-byte aligned memory boundaries, as the patch explicitly addresses this alignment requirement. When multi-buffer configurations are implemented later in the setup process, the existing validation logic fails to account for the additional memory overhead required for proper frame management.
The mitigation strategy implemented in this patch establishes a minimum headroom requirement of 128 bytes to align with typical hardware memory alignment patterns while also accounting for tailroom space requirements. This approach ensures that allocated memory regions can properly accommodate both the minimum-sized ethernet frames and the necessary metadata structures. The fix specifically tightens the validation process to prevent scenarios where insufficient headroom would lead to frame corruption during packet processing operations. This solution directly addresses the CWE-129 vulnerability category related to insufficient validation of array indices and memory access violations. The patch also aligns with ATT&CK technique T1059.003 for execution through system commands, as proper memory allocation prevents potential exploitation vectors that could arise from memory corruption during network packet processing operations. The enhanced validation mechanism ensures that XDP applications can reliably process network traffic without encountering memory allocation failures that could compromise system stability or security.