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CVE-2026-90402
bus: mhi: host: Fix controller cleanup on EDL sysfs failure
Published 2026-09-17 (31 days ago) by the Linux kernel CNA. Subsystem drivers/bus. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-90402 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
mhi_register_controller() adds the controller device before creating the optional trigger_edl sysfs file. If sysfs_create_file() fails, the error path only drops the device reference and leaves the device registered. Hence, call device_del() in the error path before put_device().
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
drivers/bus/mhi/host/init.c
- What this is
- MHI BUSMAINTAINERS section matched on drivers/bus/mhi/ · mhi@lists.linux.dev · Maintained
- Kernel module
- mhi
Check it on the machine
grep -w CONFIG_MHI_BUS /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w mhiPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sid, bookworm · linux-6.12m
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switch
- CONFIG_MHI_BUS
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-09-17 (31 days ago)source
- CVSS
- 7.0 high
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.12%, higher than 1.8% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- drivers/bus
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.10 | 6.12.110 | 7943dc67250f |
| 6.10 | 6.18.52 | 4fb17a7c437f |
| 6.10 | 7.2.6 | 4743959aa8d8 |
| 6.10 | 7.3 | 0d5b9e66591d |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The missing device_del() is in mhi_register_controller() after device_add(), reached from mhi_pci_probe() for EDL-capable PCI WWAN controllers that set edl_trigger (Qualcomm SDX/QDU). The leftover mhi_dev is then opened via local sysfs; sysfs_create_file(trigger_edl) is not fed by a remote protocol message.
- AC:HAttack complexity, high
- The broken err_release_dev path runs only when sysfs_create_file(&mhi_dev->dev.kobj, &dev_attr_trigger_edl.attr) fails after device_add() succeeded. That helper fails on kernfs errors such as -ENOMEM; a later mhi_pci_probe retries device_add("mhi%d") and gets -EEXIST instead, so the attacker cannot reliably re-enter this exact failure.
- PR:LPrivileges required, low
- device_add() installs mhi_dev_groups before trigger_edl is created, so serial_number and oem_pk_hash exist as DEVICE_ATTR_RO (0444) on /sys/bus/mhi/devices/mhiN/. After probe failure those files remain; an unprivileged local user can read them with no CAP_SYS_ADMIN and no user-namespace capability.
- UI:NUser interaction, none
- The attacker reads the leftover /sys/bus/mhi/devices/mhiN/serial_number or oem_pk_hash (or writes soc_reset) themselves. No second user must plug the WWAN card, mount media, or confirm a prompt.
- S:UScope, unchanged
- On the failed mhi_pci_probe(), device_unbind_cleanup() frees mhi_pdev via devres_release_all() while the still-registered mhi_dev stays a child of the PCI device. That is a host-kernel use-after-free of struct mhi_controller, not a VM, IOMMU, or sandbox escape.
- C:HConfidentiality impact, high
- Without device_del(), mhi_dev remains in sysfs with mhi_dev->mhi_cntrl pointing at mhi_pdev freed on probe failure. serial_number_show reads mhi_cntrl->serial_number from that freed object, and oem_pk_hash_show calls mhi_read_reg() on it, disclosing kernel memory.
- I:HIntegrity impact, high
- oem_pk_hash_show calls mhi_read_reg(), which invokes the freed mhi_cntrl->read_reg function pointer; soc_reset_store calls mhi_soc_reset() which uses mhi_cntrl->write_reg/reset. Replacing the freed struct mhi_controller yields an arbitrary call/write primitive for control-flow hijack.
- A:HAvailability impact, high
- serial_number_show, oem_pk_hash_show, and soc_reset_store dereference the dangling mhi_cntrl and oops or panic. The leaked device also keeps the mhiN name while ida_free() reuses the index, so a later mhi_register_controller() device_add() fails until reboot.