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CVE-2026-74647
misc: fastrpc: Remove buffer from list prior to unmap operation
Published 2026-08-22 (2 months ago) by the Linux kernel CNA. Subsystem drivers/misc. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-74647 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-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6466-1 · 2026-08-25 · text | 6.12.105-1 | Update the kernel and reboot. DSA-6466-1 shipped the fix on 2026-08-25, in 6.12.105-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
fastrpc_req_munmap_impl() is called to unmap any buffer. The buffer is getting removed from the list after it is unmapped from DSP. This can create potential race conditions if multiple threads invoke unmap concurrently, where one thread may remove the entry from the list while another thread's unmap operation is still ongoing. Fix this by removing the buffer entry from the list before calling the unmap operation. If the unmap fails, the entry is re-added to the list so that userspace can retry the unmap, or alternatively, the buffer will be cleaned up during device release when the DSP process is torn down and all DSP-side mappings are freed along with remaining buffers in the list.
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/misc/fastrpc.c
- What this is
- QUALCOMM FASTRPC DRIVERMAINTAINERS section matched on drivers/misc/fastrpc.c · linux-arm-msm@vger.kernel.org · Maintained
- Kernel module
- fastrpc
Check it on the machine
grep -w CONFIG_QCOM_FASTRPC /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 fastrpcPrints 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 does not build this code in 1 release. It does build it in 4 releases, so the answer depends on which release the machine runs.
- bookwormn
- trixieMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/cloud-arm64, armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- forky, sidMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt-amd64, arm64/cloud-arm64, armhf/armmp, armhf/armmp-lpae, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- bookworm · linux-6.12Mnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/cloud-arm64, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k
- n
- not enabled on any flavour - this release does not build the code
- M
- a module where it is built at all; some flavours do not build it
- Build switch
- CONFIG_QCOM_FASTRPC
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
- 2026-08-22 (2 months 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
- 0.18%, higher than 6.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/misc
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.5 | 5.10.267 | 1edb654b2b41 |
| 5.5 | 5.15.218 | 4716c23c206a |
| 5.5 | 6.1.185 | 99f8de36c84c |
| 5.5 | 6.6.152 | 97273624f7b3 |
| 5.5 | 6.12.104 | fe7032905597 |
| 5.5 | 6.18.45 | 9bf22a7d950c |
| 5.5 | 7.1.9 | 0beaa9bd7eb1 |
| 5.5 | 7.2 | 6102ceb4eab8 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DSA-6466-1 | 2026-08-25 | trixie 6.12.105-1 | 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 flaw is reachable only through local ioctl on a FastRPC misc device (/dev/fastrpc-*); entry is open() plus FASTRPC_IOCTL_MUNMAP after mmap, not via network, Bluetooth, WiFi, or physical buses.
- AC:LAttack complexity, low
- An attacker controls both racing threads and can repeatedly issue concurrent MUNMAP ioctls for the same mapped buffer; the pre-fix window spans the full DSP unmap in fastrpc_req_munmap_impl(), so no attacker-uncontrollable timing is required.
- PR:LPrivileges required, low
- The MMAP/MUNMAP ioctl path has no capable() or init-namespace root check; on Qualcomm/Android phones an unprivileged app that can open the non-secure FastRPC node and create an unsigned user PD can reach this code.
- UI:NUser interaction, none
- Exploitation needs only attacker-controlled open/ioctl and pthread scheduling against a buffer it already mapped; no separate victim action such as mounting a filesystem or opening a file is required.
- S:UScope, unchanged
- The race corrupts kernel list/slab state and double-frees struct fastrpc_buf inside the host kernel driver, matching other FastRPC kernel memory-safety CVEs rather than an inherent VM escape or IOMMU boundary bypass.
- C:HConfidentiality impact, high
- Concurrent unmap can UAF the list node and double-free a fastrpc_buf slab object holding DMA mapping metadata, a classic kernel primitive that can be groomed into arbitrary kernel memory disclosure.
- I:HIntegrity impact, high
- Double kfree of fastrpc_buf plus repeated dma_free_coherent on the same coherent mapping enables heap corruption and plausible control-flow or arbitrary-write exploitation in kernel context.
- A:HAvailability impact, high
- Winning the race can trigger list_del on freed memory, slab double-free, or DMA allocator corruption, producing kernel warnings, oopses, or panics that are repeatable via local ioctl flooding.