VulnerabilityPublished 3 Jul 2025Updated 5 Nov 2026

CVE-2025-38170: Linux kernel · arm64/fpsimd: Discard stale CPU state when handling SME traps

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in de89368de3894a8db27caeb8fd902ba1c49f696a : update Linux kernel when convenient.

Data as of 5 Nov 2026, 21:04 UTC

Severity

Unrated

Rated by Threat Radar · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-05.

Patch

Available – fixed in de89368de3894a8db27caeb8fd902ba1c49f696a, d3eaab3c70905c5467e5c4ea403053d67505adeb, c4a4786d93e99517d6f10ed56b9ffba4ce88d3b3 +2

Exploitation evidence

Disclosed: evidence found.
CVE published 3 Jul 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 8bd7f91c03d886f41d35f6108078d20be5a4a1bd, < de89368de3894a8db27caeb8fd902ba1c49f696a	Fixed in de89368de3894a8db27caeb8fd902ba1c49f696a
LinuxLinux	Affected ≥ 8bd7f91c03d886f41d35f6108078d20be5a4a1bd, < d3eaab3c70905c5467e5c4ea403053d67505adeb	Fixed in d3eaab3c70905c5467e5c4ea403053d67505adeb
LinuxLinux	Affected ≥ 8bd7f91c03d886f41d35f6108078d20be5a4a1bd, < c4a4786d93e99517d6f10ed56b9ffba4ce88d3b3	Fixed in c4a4786d93e99517d6f10ed56b9ffba4ce88d3b3
LinuxLinux	Affected ≥ 8bd7f91c03d886f41d35f6108078d20be5a4a1bd, < 6103f9ba51a59afb5a0f32299c837377c5a5a693	Fixed in 6103f9ba51a59afb5a0f32299c837377c5a5a693
LinuxLinux	Affected ≥ 8bd7f91c03d886f41d35f6108078d20be5a4a1bd, < 43be952e885476dafb74aa832c0847b2f4f650c6	Fixed in 43be952e885476dafb74aa832c0847b2f4f650c6
LinuxLinux	Affected =5.19	Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: arm64/fpsimd: Discard stale CPU state when handling SME traps The logic for handling SME traps manipulates saved FPSIMD/SVE/SME state incorrectly, and a race with preemption can result in a task having TIF_SME set and TIF_FOREIGN_FPSTATE clear even though the live CPU state is stale (e.g. with SME traps enabled). This can result in warnings from do_sme_acc() where SME traps are not expected while TIF_SME is set: | /* With TIF_SME userspace shouldn't generate any traps */ | if (test_and_set_thread_flag(TIF_SME)) | WARN_ON(1); This is very similar to the SVE issue we fixed in commit: 751ecf6afd6568ad ("arm64/sve: Discard stale CPU state when handling SVE traps") The race can occur when the SME trap handler is preempted before and after manipulating the saved FPSIMD/SVE/SME state, starting and ending on the same CPU, e.g. | void do_sme_acc(unsigned long esr, struct pt_regs *regs) | { | // Trap on CPU 0 with TIF_SME clear, SME traps enabled | // task->fpsimd_cpu is 0. | // per_cpu_ptr(&fpsimd_last_state, 0) is task. | | ... | | // Preempted; migrated from CPU 0 to CPU 1. | // TIF_FOREIGN_FPSTATE is set. | | get_cpu_fpsimd_context(); | | /* With TIF_SME userspace shouldn't generate any traps */ | if (test_and_set_thread_flag(TIF_SME)) | WARN_ON(1); | | if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) { | unsigned long vq_minus_one = | sve_vq_from_vl(task_get_sme_vl(current)) - 1; | sme_set_vq(vq_minus_one); | | fpsimd_bind_task_to_cpu(); | } | | put_cpu_fpsimd_context(); | | // Preempted; migrated from CPU 1 to CPU 0. | // task->fpsimd_cpu is still 0 | // If per_cpu_ptr(&fpsimd_last_state, 0) is still task then: | // - Stale HW state is reused (with SME traps enabled) | // - TIF_FOREIGN_FPSTATE is cleared | // - A return to userspace skips HW state restore | } Fix the case where the state is not live and TIF_FOREIGN_FPSTATE is set by calling fpsimd_flush_task_state() to detach from the saved CPU state. This ensures that a subsequent context switch will not reuse the stale CPU state, and will instead set TIF_FOREIGN_FPSTATE, forcing the new state to be reloaded from memory prior to a return to userspace. Note: this was originallly posted as [1]. [ Rutland: rewrite commit message ]

References

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