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CVE-2026-74646
misc: fastrpc: take fl->lock when moving mmaps on interrupted invoke
Published 2026-08-22 (2 months ago) by the Linux kernel CNA. Subsystem drivers/misc. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-74646 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-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
When an invoke is interrupted by a signal, wait_for_completion_interruptible() returns -ERESTARTSYS and fastrpc_internal_invoke() moves every buffer from fl->mmaps onto cctx->invoke_interrupted_mmaps. This list_del()/list_add_tail() walk runs without holding fl->lock, the lock that serialises fl->mmaps in fastrpc_req_mmap() and fastrpc_req_munmap() everywhere else. Take fl->lock around the move, matching every other fl->mmaps accessor.
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
- unimportantsource
- 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 |
|---|---|---|
| 6.2 | 6.6.152 | 3f265e405e5e |
| 6.2 | 6.12.104 | a902fe1f80f5 |
| 6.2 | 6.18.45 | af6345159abc |
| 6.2 | 7.1.9 | efd02f8d1a74 |
| 6.2 | 7.2 | b85a0e91d7d6 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | 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
- Reachable only through local ioctl on the Qualcomm FastRPC miscdevice (/dev/fastrpc-*); communication with the DSP is internal rpmsg/glink IPC on the SoC, not via network or adjacent wireless protocols.
- AC:LAttack complexity, low
- Attacker controls both sides: one thread blocks in FASTRPC_IOCTL_INVOKE, delivers a signal to force -ERESTARTSYS, and another thread issues concurrent FASTRPC_IOCTL_MMAP/MUNMAP on the same fd; the race can be retried until it wins.
- PR:LPrivileges required, low
- fastrpc_device_ioctl has no capability check; on Qualcomm/Android deployments non-root processes with FastRPC device access (HALs, system services, or unsigned-PD offload clients) can open the node and hit the vulnerable path without real root.
- UI:NUser interaction, none
- No victim interaction is required beyond the attacker's own local access; exploitation uses attacker-controlled threads and signals to race ioctls on an already-open FastRPC file descriptor.
- S:UScope, unchanged
- The bug corrupts kernel linked-list/heap state in the host OS FastRPC driver; impact is local kernel privilege escalation within the same security authority, not a VM escape or IOMMU boundary bypass.
- C:HConfidentiality impact, high
- Unsynchronized list_del/list_add_tail on fl->mmaps corrupts kernel list pointers and can orphan or double-reference fastrpc_buf objects, enabling use-after-free and kernel memory disclosure primitives.
- I:HIntegrity impact, high
- Corrupting mmap tracking list nodes in kernel heap can yield double-free or use-after-free of fastrpc_buf slabs, which are standard primitives for arbitrary kernel write and control-flow hijacking.
- A:HAvailability impact, high
- List corruption on fl->mmaps reliably causes kernel oops/panic during subsequent mmap/munmap or user teardown; repeated ioctl racing can crash or hang the device.