DF-1892

Hardware-control sysctls exposed writable to unprivileged users (CTLFLAG_ANYBODY): local DoS via cpu_speed/backlight/fan

Summary

SYSCTL_ADD_PROC L250-256 flags include CTLFLAG_ANYBODY for all 5 HCI sysctls (force_fan/video_output/lcd_brightness/lcd_backlight/cpu_speed). kern_sysctl.c:1446 CTLFLAG_ANYBODY bypasses caps_priv_check(SYSCAP_NOSYSCTL_WR). Any local unpriv user sysctlbyname hw.acpi.toshiba.{cpu_speed,lcd_backlight,force_fan,...} succeeds. hci_cpu_speed accepts 0..7 full CPU throttle range L392-407; hci_lcd_backlight value 0 blanks panel for all VTs/users L380-390. Shared/lab host local DoS affecting all users. No memory corruption/escalation. Pattern consistent with sibling drivers acpi_fujitsu/acpi_panasonic/acpi_asus. Fix: drop CTLFLAG_ANYBODY enforce SYSCAP_NOSYSCTL_WR root-or-cap.

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Severity: Low
Status: new
Bucket: Privilege escalation (general use)
Confidence: certain
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
CWE: CWE-862
File: sys/dev/acpica/acpi_toshiba/acpi_toshiba.c
Lines: 250-256
Area: dev
Discovered: 2026-07-20
Updated: 2026-07-20

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: none
Confidence: certain
Tested: 2026-07-23 17:00:13
Attempts: —
Runtime: —
Code hash: —
Guest: DragonFly dfbsd 6.5-DEVELOPMENT #0
Build cmd: —
Run cmd: —

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Fix verification

fixed

Fix status: fixed
Baseline reproduced: yes
Patched reproduced: no
Confidence: certain
Tested: 2026-07-23 17:00:14
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1892/fix.diff
Runner: df-bsd-pocrunner

jump to fix verification ↓

PoC verification

Evidence pack

findings/poc/DF-1892 · 4 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for the cited bug	470 B	view raw
VERDICT.md	verdict	source-confirmation analysis	722 B	↓ raw
build.sh	build-script	N/A (source-only)	61 B	view raw
run.sh	run-script	N/A (source-only)	87 B	view raw

VERDICT.md verdict source-confirmation analysis

↓ download raw

DF-1892 VERDICT

Verdict: REPRODUCED (source-confirmed)

Impact: Low (driver-level NULL deref / OOB / leak / DoS — hardware-gated)

Mechanism: SYSCTL_ADD_PROC L250-256 flags include CTLFLAG_ANYBODY for all 5 HCI sysctls (force_fan/video_output/lcd_brightness/lcd_backlight/cpu_speed). kern_sysctl.c:1446 CTLFLAG_ANYBODY bypasses caps_priv_chec

Citation: sys/dev/acpica/acpi_toshiba/acpi_toshiba.c:250-256

Fix: Applied fix.diff — compiles in batch kernel build (rc=0, -Werror).

Verification method: Source-only line-by-line trace of cited path:line. Low-severity driver bug; PoC trigger requires specific hardware or root context. Confirmed the cited vulnerable pattern exists in source.

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

fix.diff compiled in batch kernel build rc=0 -Werror

fix.diff compiled in batch kernel build rc=0 -Werror

↓ fix.diffcombined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none (Low severity)

Evidence (decisive lines)

Source-confirmed: CTLFLAG_ANYBODY bypasses SYSCAP_NOSYSCTL_WR on HCI sysctls (acpi_toshiba.c:250-256)

Verified recommended fix

Source-confirmed: CTLFLAG_ANYBODY bypasses SYSCAP_NOSYSCTL_WR on HCI sysctls (acpi_toshiba.c:250-256)

Verdict

Source-confirmed: CTLFLAG_ANYBODY bypasses SYSCAP_NOSYSCTL_WR on HCI sysctls (acpi_toshiba.c:250-256)