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CVE-2026-89597
fbdev: uvesafb: unregister connector callback on init failure
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem drivers/video. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89597 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
uvesafb_init() registers the v86d connector callback before registering the platform driver. If platform_driver_register() fails, the function returns the error directly and leaves the connector callback registered. The later platform-device failure path already unregisters the callback. Add the same cleanup before the final return when platform-driver registration fails. This issue was identified during our ongoing static-analysis research while reviewing kernel code.
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/video/fbdev/uvesafb.c
- What this is
- UVESAFB DRIVERMAINTAINERS section matched on drivers/video/fbdev/uvesafb.* · linux-fbdev@vger.kernel.org · Maintained
- Kernel module
- uvesafb
Check it on the machine
grep -w CONFIG_FB_UVESA /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 uvesafbPrints 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/arm64, arm64/cloud-arm64, arm64/rt/arm64, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le
- trixieMnot built on amd64/cloud-amd64, arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt/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/cloud-amd64, arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt-arm64, armhf/armmp, armhf/armmp-lpae, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt/arm64, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k
- M
- a module where it is built at all; some flavours do not build it
- Build switch
- CONFIG_FB_UVESA
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/video
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.24 | 5.10.270 | b149f77d0408 |
| 2.6.24 | 5.15.221 | 0352fdac3cbf |
| 2.6.24 | 6.1.188 | 17518e7123f7 |
| 2.6.24 | 6.6.157 | 9eb7b3cbe99c |
| 2.6.24 | 6.12.109 | 9f8a822b44c4 |
| 2.6.24 | 6.18.50 | 466a8af0dee2 |
| 2.6.24 | 7.2.4 | 9e768ae51426 |
| 2.6.24 | 7.3 | de8db23aa7c3 |
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 v86d connector callback is reached only via a local NETLINK_CONNECTOR socket: cn_rx_skb() -> cn_call_callback() invokes the registered handler. There is no remote packet, Bluetooth/WiFi, or USB path into this code.
- AC:LAttack complexity, low
- Once platform_driver_register() fails, cn_add_callback() has already left uvesafb_cn_callback on the global connector list while free_module() unmaps the driver. A single NETLINK_CONNECTOR message with CN_IDX_V86D/CN_VAL_V86D_UVESAFB then calls that stale pointer with no race or other condition beyond the attacker's control.
- PR:LPrivileges required, low
- Unprivileged users may create NETLINK_CONNECTOR sockets and send to kernel portid 0 without CAP_NET_ADMIN. The callback's capable(CAP_SYS_ADMIN) check never runs because the UAF occurs at the call through the freed module text, so init-namespace root is not required.
- UI:NUser interaction, none
- The attacker sends the netlink message from their own process. No separate victim action such as mounting a filesystem, opening a device node, or loading a module is required to hit the dangling callback.
- S:UScope, unchanged
- The stale function pointer and freed uvesafb module memory are kernel-side resources in the same security authority. This is local privilege escalation, not VM escape, IOMMU bypass, or another cross-boundary impact.
- C:HConfidentiality impact, high
- The leftover cn_callback_entry still points at uvesafb_cn_callback in freed module text. That use-after-free lets an attacker reclaim the pages and obtain an arbitrary kernel read primitive.
- I:HIntegrity impact, high
- Calling through a function pointer that resides in freed module memory is a control-flow hijack once those pages are reallocated, giving an arbitrary write and code-execution primitive.
- A:HAvailability impact, high
- Invoking the stale connector callback jumps into unmapped or reused module text and reliably oopses or panics the kernel even if the attacker does not fully exploit the UAF.