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CVE-2026-63797
rpmsg: char: Fix use-after-free on probe error path
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem drivers/rpmsg. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-63797 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-4720-1 · 2026-08-05 · text | 6.1.180-1 | Update the kernel and reboot. DLA-4720-1 shipped the fix on 2026-08-05, in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.95-1 | Update the kernel and reboot. Fixed in 6.12.95-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.3-1 | Update the kernel and reboot. Fixed in 7.1.3-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.3-1 | Update the kernel and reboot. Fixed in 7.1.3-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
rpmsg_chrdev_probe() stores the newly allocated eptdev in the default endpoint's priv pointer before calling rpmsg_chrdev_eptdev_add(). If rpmsg_chrdev_eptdev_add() then fails, its error path frees eptdev while the default endpoint may still dispatch callbacks with the stale priv pointer. Avoid publishing eptdev through the default endpoint until rpmsg_chrdev_eptdev_add() succeeds. Messages received before the priv pointer is published should be ignored by rpmsg_ept_cb(). Flow-control updates can hit rpmsg_ept_flow_cb() in the same window, so make both callbacks return success when priv is NULL.
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/rpmsg/rpmsg_char.c
- What this is
- REMOTE PROCESSOR MESSAGING (RPMSG) SUBSYSTEMMAINTAINERS section matched on drivers/rpmsg/ · linux-remoteproc@vger.kernel.org · Maintained
- Kernel module
- rpmsg_char
Check it on the machine
grep -wE 'CONFIG_RPMSG|CONFIG_RPMSG_CHAR' /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 rpmsg_charPrints 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/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/arm64, arm64/cloud-arm64, arm64/rt/arm64, i386/686, i386/686-pae, i386/rt/686-pae, ppc64el/powerpc64le
- trixieMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt/arm64, armel/rpi, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- forky, sidMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt-amd64, arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt-arm64, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_RPMSG, CONFIG_RPMSG_CHAR
- Reads as
- all on means the file is compiled; any one off means it is not.
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
- 2026-07-19 (3 months ago)source
- CVSS
- 8.4 high
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.15%, higher than 3.4% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/rpmsg
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.18 | 6.1.178 | 1306fc4f76f7 |
| 5.18 | 6.6.144 | ddf13f91ca82 |
| 5.18 | 6.12.95 | c5ebb06c7e24 |
| 5.18 | 6.18.38 | 104d10021239 |
| 5.18 | 7.1.3 | ff268cd9ccbc |
| 5.18 | 7.2 | 1ff3f528e67d |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4723-1 | 2026-08-07 | bullseye 6.1.180-1~deb11u1 | tracker |
| DLA-4720-1 | 2026-08-05 | bookworm 6.1.180-1 | 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 vulnerable code is in the rpmsg char driver and is reached when a coprocessor sends IPC messages over virtio/glink/SMD after announcing an rpmsg-raw channel; this is on-chip inter-processor communication, not a network-facing kernel protocol.
- AC:LAttack complexity, low
- A compromised or malicious remote processor controls both channel announcements (to force probe failure via minor exhaustion) and the timing of inbound messages that invoke the stale priv pointer, making the race reliably attacker-driven.
- PR:NPrivileges required, none
- Exploitation requires no Linux credentials; a compromised remote processor (modem, DSP, Cortex-M firmware) can announce rpmsg-raw channels and send messages without any local user or root access on the AP.
- UI:NUser interaction, none
- No victim user action is required; the remote processor initiates channel creation and message delivery autonomously through the rpmsg name service and messaging bus.
- S:UScope, unchanged
- The UAF corrupts kernel heap memory on the application processor, enabling privilege escalation within the kernel security boundary rather than crossing a VM or IOMMU isolation boundary.
- C:HConfidentiality impact, high
- The use-after-free dereferences a freed kmalloc object to access queue_lock, skb queue heads, and wait queues, providing attacker-influenced heap reads that can be leveraged for arbitrary kernel memory disclosure.
- I:HIntegrity impact, high
- The UAF writes to fields in the freed rpmsg_eptdev structure (spinlock, skb queue, flow-control flags, wait queue), enabling heap corruption primitives that can be developed into arbitrary kernel writes or code execution.
- A:HAvailability impact, high
- Use-after-free access to freed eptdev memory can cause kernel oops/panic from corrupting spinlocks and wait queues, and repeated triggering by the remote processor enables sustained denial of service.