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CVE-2026-89440
mmc: via-sdmmc: stop card-detect handling on probe failure
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem drivers/mmc. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89440 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 | fixedDLA-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| 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
request_irq() registers the SD card-detect interrupt and the probe enables it before mmc_add_host() runs. If mmc_add_host() fails, the error path only unmaps the registers and returns: the interrupt stays registered, so the handler keeps running against the host once it is freed. via_sdc_isr() dereferences sdhost and its MMIO base and schedules carddet_work, which via_sdc_card_detect() also runs against freed memory through its container_of() dereference. Add a probe-error path that disables and frees the interrupt and cancels carddet_work before unmapping. carddet_work can re-enable the device interrupt via via_reset_pcictrl(), which restores PCIINTCTRL, so mask it again after cancelling the work. This issue was found by an in-house static analysis tool and confirmed by manual code review.
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/mmc/host/via-sdmmc.c
- What this is
- MULTIMEDIA CARD (MMC), SECURE DIGITAL (SD) AND SDIO SUBSYSTEMMAINTAINERS section matched on drivers/mmc/ · linux-mmc@vger.kernel.org · Maintained
- Kernel module
- via_sdmmc
Check it on the machine
grep -w CONFIG_MMC_VIA_SDMMC /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 via_sdmmcPrints 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, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormMnot built on amd64/cloud-amd64, arm64/cloud-arm64
- trixieMnot built on amd64/cloud-amd64, arm64/cloud-arm64, armel/rpi, s390x/s390x
- forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64, loong64/loong64, s390x/s390x
- bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switch
- CONFIG_MMC_VIA_SDMMC
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
- 2026-09-11 (37 days ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 5.8% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/mmc
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.10.163 | 5.10.270 | 5bb5327b92aa |
| 5.15.86 | 5.15.221 | d045596706d1 |
| 6.1.2 | 6.1.188 | 806409f12fdb |
| 6.2 | 6.6.157 | dde5b9c91e9f |
| 6.2 | 6.12.109 | efe7f25dd27e |
| 6.2 | 6.18.50 | 2550f89589ca |
| 6.2 | 7.2.4 | c2b8a6249119 |
| 6.2 | 7.3 | 088eaa92fceb |
| 4.9.337 | 0 | 0 |
| 4.14.303 | 0 | 0 |
| 4.19.270 | 0 | 0 |
| 5.4.229 | 0 | 0 |
| 6.0.16 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| 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 leftover IRQ use-after-free is in the VIA VT9530 PCI SD/MMC host probe path (via_sd_probe enabling via_sdc_isr before mmc_add_host) on systems that already have this onboard/PCI reader; it is not reached by network packets or USB hotplug.
- AC:LAttack complexity, low
- The driver arms the shared card-detect IRQ before mmc_add_host(); a failed add leaves via_sdc_isr registered against freed sdhost indefinitely, so a local attacker who induces device_add failure (memory pressure/reprobe) and reclaims the host slab does not depend on an uncontrolled race.
- PR:LPrivileges required, low
- An unprivileged local user on a machine with this PCI reader can be present when probe fails and then spray the heap while the dangling shared IRQ fires; capability-gated PCI sysfs unbind is not required for the UAF itself, so PR:L is the higher-severity defensible bar.
- UI:NUser interaction, none
- No victim action such as inserting an SD card, mounting media, or opening a file is required; after failed probe the leftover ISR and carddet_work run from hardware or shared interrupts without another user's involvement.
- S:UScope, unchanged
- The use-after-free corrupts kernel heap and IRQ/workqueue state inside the host OS; this is standard in-kernel memory corruption, not a VM escape, IOMMU/DMA isolation bypass, or other cross-authority breakout.
- C:HConfidentiality impact, high
- via_sdc_isr spin_locks and dereferences the freed via_crdr_mmc_host (MMIO bases and status registers) and may queue carddet_work that recovers the same object via container_of(), a kernel UAF that enables arbitrary disclosure via slab reuse.
- I:HIntegrity impact, high
- The same UAF lets a reclaimed host object supply lock, MMIO, and work pointers used for MMIO writes, work scheduling, and via_reset_pcictrl, enabling heap spraying and control-flow hijack rather than a crash-only outcome.
- A:HAvailability impact, high
- IRQ-context dereference of freed sdhost after iounmap and devm mmc_free_host causes a kernel oops or panic even without full exploitation, so availability impact is High.