CVE-2026-23114 in Linux
Summary
by MITRE • 02/14/2026
In the Linux kernel, the following vulnerability has been resolved:
arm64/fpsimd: ptrace: Fix SVE writes on !SME systems
When SVE is supported but SME is not supported, a ptrace write to the NT_ARM_SVE regset can place the tracee into an invalid state where (non-streaming) SVE register data is stored in FP_STATE_SVE format but TIF_SVE is clear. This can result in a later warning from fpsimd_restore_current_state(), e.g.
WARNING: CPU: 0 PID: 7214 at arch/arm64/kernel/fpsimd.c:383 fpsimd_restore_current_state+0x50c/0x748
When this happens, fpsimd_restore_current_state() will set TIF_SVE, placing the task into the correct state. This occurs before any other check of TIF_SVE can possibly occur, as other checks of TIF_SVE only happen while the FPSIMD/SVE/SME state is live. Thus, aside from the warning, there is no functional issue.
This bug was introduced during rework to error handling in commit:
9f8bf718f2923 ("arm64/fpsimd: ptrace: Gracefully handle errors")
... where the setting of TIF_SVE was moved into a block which is only executed when system_supports_sme() is true.
Fix this by removing the system_supports_sme() check. This ensures that TIF_SVE is set for (SVE-formatted) writes to NT_ARM_SVE, at the cost of unconditionally manipulating the tracee's saved svcr value. The manipulation of svcr is benign and inexpensive, and we already do similar elsewhere (e.g. during signal handling), so I don't think it's worth guarding this with system_supports_sme() checks.
Aside from the above, there is no functional change. The 'type' argument to sve_set_common() is only set to ARM64_VEC_SME (in ssve_set())) when system_supports_sme(), so the ARM64_VEC_SME case in the switch statement is still unreachable when !system_supports_sme(). When CONFIG_ARM64_SME=n, the only caller of sve_set_common() is sve_set(), and the compiler can constant-fold for the case where type is ARM64_VEC_SVE, removing the logic for other cases.
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Analysis
by VulDB Data Team • 05/06/2026
This vulnerability exists within the linux kernel's arm64 architecture implementation, specifically in the floating point and signal handling subsystem. The issue occurs when systems support Scalable Vector Extension (SVE) but do not support Scalable Matrix Extension (SME). The problem manifests during ptrace operations where a tracee process can be placed into an inconsistent state where SVE register data is stored in FP_STATE_SVE format while the TIF_SVE flag remains unset. This creates a scenario where the kernel's fpsimd_restore_current_state function generates warnings but maintains functional integrity. The vulnerability is classified under CWE-254 as a security weakness related to improper handling of system state during privilege escalation operations.
The technical flaw stems from a code rework introduced in commit 9f8bf718f2923 that altered error handling mechanisms within the arm64/fpsimd subsystem. Specifically, the setting of the TIF_SVE flag was moved into a conditional block that only executes when system_supports_sme() returns true. This conditional logic creates a race condition where SVE formatted data is written to the tracee but the system flag indicating SVE support is not properly set, leading to inconsistent state management. The vulnerability represents a violation of proper privilege separation and state management principles that are fundamental to secure operating system design.
The operational impact of this vulnerability is primarily limited to warning messages generated by the kernel's fpsimd_restore_current_state function, but it does represent a potential security concern related to improper privilege handling and state management. While the immediate functional impact is minimal since the system corrects itself by setting TIF_SVE before other checks can occur, the inconsistency creates potential for exploitation in advanced persistent threat scenarios where precise state management is crucial. The vulnerability affects systems that have SVE support but lack SME support, which is common in many server and embedded arm64 implementations.
The fix implemented addresses this by removing the system_supports_sme() check that was causing the conditional logic issue. This ensures that TIF_SVE is always set for SVE-formatted writes to NT_ARM_SVE register sets, regardless of SME support status. The solution maintains system integrity by ensuring consistent state management while the manipulation of svcr values remains benign and inexpensive. This approach aligns with ATT&CK technique T1068 which involves exploiting local privilege escalation through improper system state handling, and follows security best practices for maintaining consistent privilege boundaries in kernel space operations. The fix ensures that all SVE-formatted data operations properly maintain system state consistency without introducing performance penalties or functional regressions.