CVE-2026-98249 in Linux
Summary
by MITRE • 10/06/2026
In the Linux kernel, the following vulnerability has been resolved:
arm64: hibernate: pass HVC_SET_VECTORS args to the resume hvc
swsusp_arch_suspend_exit() reinstalls the restored kernel's hyp stub vectors with an hvc, but never passes the arguments. x0 is not set to HVC_SET_VECTORS and x1 is not set to the vector address, so the stub dispatch falls through and returns without writing vbar_el2. EL2 is left pointing at the trans_pgd copy of the vectors, a page that swsusp_free() releases right after resume.
Set the arguments up the same way __hyp_set_vectors() does.
Without this fix, Vladimir was able to trigger a hang when resuming from hibernation with CONFIG_PAGE_POISONING=y and page_poison=on.
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Analysis
by VulDB Data Team • 10/06/2026
The Linux kernel for ARM64 architectures contains a critical flaw in the system suspend and resume mechanism related to hypervisor vector management during hibernation transitions. The vulnerability resides within the swsusp_arch_suspend_exit function, which is responsible for restoring the kernel's state after resuming from a suspended or hibernated state. Specifically, this routine attempts to reinstall the restored kernel's hyp stub vectors using an HVC (Hypervisor Call) instruction. However, the implementation fails to correctly initialize the processor registers required by the hypervisor entry point before executing the call. This oversight results in the hyp stub dispatch logic receiving invalid or uninitialized arguments, causing it to fall through without performing its intended function of updating the Vector Base Address Register at exception level two (VBAR_EL2).
From a technical perspective, the ARM64 architecture relies on specific register conventions for HVC instructions to communicate with the EL2 hypervisor. The x0 register must contain the command identifier, which in this context is HVC_SET_VECTORS, and the x1 register must hold the physical address of the new vector table. Because these registers are not explicitly set prior to the hvc instruction execution, the hyp stub does not recognize the request as a valid vector update operation. Consequently, VBAR_EL2 remains pointed at the previous memory location rather than being updated to reflect the restored kernel's vectors. This creates a state where the processor is still referencing old or invalid exception handling paths immediately after resume operations begin.
The operational impact of this vulnerability manifests primarily during the resumption phase from hibernation. When CONFIG_PAGE_POISONING is enabled along with the page_poison boot parameter, the system relies on strict memory integrity checks to detect corruption and ensure security boundaries are maintained. Without the correct vector update, the resumed kernel may attempt to execute code or handle exceptions using stale pointers that point to trans_pgd copies of vectors. These specific pages are scheduled for release by swsusp_free immediately following the resume process. Accessing freed memory leads to undefined behavior, which in observed cases results in a complete system hang rather than a graceful error return. This effectively denies service and prevents the device from becoming operational after hibernation cycles.
This issue aligns with CWE-20 Improper Input Validation as it involves failing to properly validate or set up required input parameters for a critical system call, leading to unexpected execution paths. Furthermore, in terms of ATT&CK mapping, this vulnerability relates to techniques involving persistence and privilege escalation through kernel exploitation if an attacker can trigger the hibernation cycle under specific conditions, although its primary impact here is availability disruption via denial of service during resume operations. The failure to update VBAR_EL2 represents a breakdown in state consistency between EL1 and EL2 execution environments.
To mitigate this vulnerability, developers must ensure that swsusp_arch_suspend_exit correctly initializes the x0 and x1 registers with HVC_SET_VECTORS and the appropriate vector address respectively before invoking the hyp stub. This aligns the resume path behavior with the standard __hyp_set_vectors implementation used elsewhere in the kernel codebase. System administrators should apply patches that include this fix to prevent system hangs during hibernation resumes, particularly on configurations where page poisoning is active for security auditing purposes. Regular updates to the Linux kernel are essential to maintain stability and security across ARM64-based devices relying on advanced power management features.