medium 5.5

CVE-2026-23107 json

arm64/fpsimd: signal: Allocate SSVE storage when restoring ZA

published 2026-02-04 9 mo ago modified 2026-11-05 3 d ago also EUVD-2026-5434

cvss: 5.5; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.2%; EPSS 0.2% chance of exploitation in 30 days, percentile 4%
public exploits: 0; none known

In the Linux kernel, the following vulnerability has been resolved:

The code to restore a ZA context doesn't attempt to allocate the task's sve_state before setting TIF_SME. Consequently, restoring a ZA context can place a task into an invalid state where TIF_SME is set but the task's sve_state is NULL.

In legitimate but uncommon cases where the ZA signal context was NOT created by the kernel in the context of the same task (e.g. if the task is saved/restored with something like CRIU), we have no guarantee that sve_state had been allocated previously. In these cases, userspace can enter streaming mode without trapping while sve_state is NULL, causing a later NULL pointer dereference when the kernel attempts to store the register state:

| # ./sigreturn-za | Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 | Mem abort info: | ESR = 0x0000000096000046 | EC = 0x25: DABT (current EL), IL = 32 bits | SET = 0, FnV = 0 | EA = 0, S1PTW = 0 | FSC = 0x06: level 2 translation fault | Data abort info: | ISV = 0, ISS = 0x00000046, ISS2 = 0x00000000 | CM = 0, WnR = 1, TnD = 0, TagAccess = 0 | GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 | user pgtable: 4k pages, 52-bit VAs, pgdp=0000000101f47c00 | [0000000000000000] pgd=08000001021d8403, p4d=0800000102274403, pud=0800000102275403, pmd=0000000000000000 | Internal error: Oops: 0000000096000046 [#1] SMP | Modules linked in: | CPU: 0 UID: 0 PID: 153 Comm: sigreturn-za Not tainted 6.19.0-rc1 #1 PREEMPT | Hardware name: linux,dummy-virt (DT) | pstate: 214000c9 (nzCv daIF +PAN -UAO -TCO +DIT -SSBS BTYPE=--) | pc : sve_save_state+0x4/0xf0 | lr : fpsimd_save_user_state+0xb0/0x1c0 | sp : ffff80008070bcc0 | x29: ffff80008070bcc0 x28: fff00000c1ca4c40 x27: 63cfa172fb5cf658 | x26: fff00000c1ca5228 x25: 0000000000000000 x24: 0000000000000000 | x23: 0000000000000000 x22: fff00000c1ca4c40 x21: fff00000c1ca4c40 | x20: 0000000000000020 x19: fff00000ff6900f0 x18: 0000000000000000 | x17: fff05e8e0311f000 x16: 0000000000000000 x15: 028fca8f3bdaf21c | x14: 0000000000000212 x13: fff00000c0209f10 x12: 0000000000000020 | x11: 0000000000200b20 x10: 0000000000000000 x9 : fff00000ff69dcc0 | x8 : 00000000000003f2 x7 : 0000000000000001 x6 : fff00000c1ca5b48 | x5 : fff05e8e0311f000 x4 : 0000000008000000 x3 : 0000000000000000 | x2 : 0000000000000001 x1 : fff00000c1ca5970 x0 : 0000000000000440 | Call trace: | sve_save_state+0x4/0xf0 (P) | fpsimd_thread_switch+0x48/0x198 | __switch_to+0x20/0x1c0 | __schedule+0x36c/0xce0 | schedule+0x34/0x11c | exit_to_user_mode_loop+0x124/0x188 | el0_interrupt+0xc8/0xd8 | __el0_irq_handler_common+0x18/0x24 | el0t_64_irq_handler+0x10/0x1c | el0t_64_irq+0x198/0x19c | Code: 54000040 d51b4408 d65f03c0 d503245f (e5bb5800) | ---[ end trace 0000000000000000 ]---

Fix this by having restore_za_context() ensure that the task's sve_state is allocated, matching what we do when taking an SME trap. Any live SVE/SSVE state (which is restored earlier from a separate signal context) must be preserved, and hence this is not zeroed.

Patch / fix

fixed in 1 distros 5 links 5

Linux Linux 6.1.162, 6.6.122, 6.12.68, 6.18.8, 6.19

debian ubuntu suse opensuse azure linux

linux Debian 12 6.1.162-1
linux Debian 13 6.12.69-1
linux Debian 14 6.18.8-1

debian advisories DEBIAN-CVE-2026-23107

linux Ubuntu 24.04 LTS 6.8.0-117.117
linux-aws Ubuntu 24.04 LTS 6.8.0-1055.58
linux-gcp Ubuntu 24.04 LTS 6.8.0-1058.61
linux-gke Ubuntu 24.04 LTS 6.8.0-1054.60
linux-ibm Ubuntu 24.04 LTS 6.8.0-1055.56
linux-azure Ubuntu 24.04 LTS 6.8.0-1056.62
linux-gkeop Ubuntu 24.04 LTS 6.8.0-1041.44
linux-raspi Ubuntu 24.04 LTS 6.8.0-1056.60

ubuntu advisories UBUNTU-CVE-2026-23107

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.34.1
kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.34.1
kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.34.1
kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.34.1
kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.34.1
kernel-zfcpdump SLE Module for Basesystem 15 SP7 6.4.0-150700.53.34.1
kernel-obs-build SLE Module for Development Tools 15 SP7 6.4.0-150700.53.34.1
kernel-default-base SLE Module for Basesystem 15 SP7 6.4.0-150700.53.34.1.150700.17.23.1

suse advisories SUSE-SU-2026:1081-1 SUSE-SU-2026:20873-1 SUSE-SU-2026:20838-1 SUSE-SU-2026:20931-1 SUSE-SU-2026:20845-1 SUSE-SU-2026:20876-1

kernel-rt openSUSE Leap 16.0 6.12.0-160000.27.1
dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.27.1
kernel-64kb openSUSE Leap 16.0 6.12.0-160000.27.1
kernel-syms openSUSE Leap 16.0 6.12.0-160000.27.1
kernel-azure openSUSE Leap 16.0 6.12.0-160000.27.1
kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.27.1
kernel-source openSUSE Leap 16.0 6.12.0-160000.27.1
kernel-default openSUSE Leap 16.0 6.12.0-160000.27.1

opensuse advisories openSUSE-SU-2026:20416-1

kernel Azure Linux 3.0 6.6.126.1-1

azure linux advisories AZL-77274

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-23107 updated 2026-11-05 cvss 6.2

kernel: Linux kernel (arm64): Denial of Service via NULL pointer dereference in ZA signal context restoration

Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
affected: no fix available
Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 3 d ago (2026-11-05)

Exploit prediction

0.15% chance of exploitation in the next 30 days, higher than 4% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
NVD	3.1	5.5	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

Linux Linux

Classification

Weakness

CWE-476 NULL Pointer Dereference

Technology feeds

Linux kernel rss critical rss

References

Sources

CVE List CVE-2026-23107
NVD CVE-2026-23107

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary