Linux Kernel up to 6.18.7 arm64 fpsimd_restore_current_state state issue

Summaryinfo

A vulnerability categorized as critical has been discovered in Linux Kernel up to 6.18.7. Affected is the function fpsimd_restore_current_state of the component arm64. Such manipulation leads to state issue. This vulnerability is traded as CVE-2026-23114. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.18.7. It has been rated as critical. Affected by this issue is the function fpsimd_restore_current_state of the component arm64. The manipulation with an unknown input leads to a state issue vulnerability. Using CWE to declare the problem leads to CWE-371. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at git.kernel.org. This vulnerability is handled as CVE-2026-23114 since 01/13/2026. The exploitation is known to be difficult. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 05/06/2026).

The vulnerability scanner Nessus provides a plugin with the ID 299176 (Linux Distros Unpatched Vulnerability : CVE-2026-23114), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.18.8 eliminates this vulnerability. Applying the patch 4f39984176e7edcaba3432b6c649c6fe93bf2f80/128a7494a9f15aad60cc6b7e3546bf481ac54a13 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (299176) and CERT Bund (WID-SEC-2026-0421). Once again VulDB remains the best source for vulnerability data.

Affected

• Google Container-Optimized OS
• Debian Linux
• Google Cloud Platform
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• SUSE openSUSE
• RESF Rocky Linux
• Open Source Linux Kernel
• IBM QRadar SIEM

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7

License

• open-source

Website

• Vendor: https://www.kernel.org/

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