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CVE-2026-89806
drm/sysfb: ofdrm: Fix integer overflow in fb_size calculation
Published 2026-09-16 (33 days ago) by the Linux kernel CNA. Subsystem drivers/gpu. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-89806 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-6568-1 · 2026-10-16 · text | 6.12.113-1 | Update the kernel and reboot. DSA-6568-1 shipped the fix on 2026-10-16, in 6.12.113-1. 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. |
The vulnerability
What the bug is
The framebuffer size calculation `fb_size = linebytes * height` can overflow when both values are large (e.g., 46341 * 46341 > INT_MAX). Since linebytes and height are both int types, the multiplication is performed as int * int, which results in undefined behavior on overflow. Use check_mul_overflow() to detect and prevent this overflow, consistent with the approach used in simpledrm.c and corebootdrm.c.
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/gpu/drm/sysfb/ofdrm.c
- What this is
- DRM DRIVER FOR FIRMWARE FRAMEBUFFERSMAINTAINERS section matched on drivers/gpu/drm/sysfb/ · dri-devel@lists.freedesktop.org · Maintained
Check it on the machine
grep -w CONFIG_DRM_OFDRM /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.
Show whether Debian builds this, per release
Debian does not build this code in 2 releases. The build rule could not be established for 2 releases, so nothing is claimed about those.
- bookworm, trixie?
- forky, sidn
- ?
- not established - no Makefile entry for the affected file
- n
- not enabled on any flavour - this release does not build the code
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switch
- CONFIG_DRM_OFDRM
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
- 2026-09-16 (33 days 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
- 0.20%, higher than 8.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- drivers/gpu
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.2 | 6.12.112 | 711fe7949d37 |
| 6.2 | 6.18.51 | ded6ad826fe0 |
| 6.2 | 7.2.5 | d9daf9a6e7a6 |
| 6.2 | 7.3 | c6f48e59ece0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DSA-6568-1 | 2026-10-16 | trixie 6.12.113-1 | 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 overflow is in ofdrm_device_create() on the local platform probe path (ofdrm_probe matching Open Firmware compatible=display); it is not reached from network protocols, Bluetooth, USB, or other remote packet handlers.
- AC:LAttack complexity, low
- An attacker who supplies OF width/linebytes/height (e.g. 46341x46341) deterministically overflows the int multiply fb_size=linebytes*height; there is no race, layout luck, or other condition outside attacker control.
- PR:NPrivileges required, none
- ofdrm_probe runs automatically from the platform bus with no capability check; a crafted display node can be supplied without an OS account via netboot/PXE, QEMU/hypervisor Open Firmware, or firmware, so no privileges on the running system are required.
- UI:NUser interaction, none
- Once a malicious display node is present, framebuffer size is computed during unattended driver probe; no victim mount, file open, or other interactive action is required.
- S:UScope, unchanged
- The overflow and resulting framebuffer mapping errors affect kernel and MMIO state on the same host; this is a standard in-kernel driver defect, not a VM escape, IOMMU bypass, or other cross-authority impact.
- C:HConfidentiality impact, high
- A wrapped fb_size ioremaps a too-small aperture while scanout still uses the attacker-chosen pitch and height, enabling out-of-bounds reads of adjacent ioremap/vmalloc memory; memory-corruption OOB access is High confidentiality.
- I:HIntegrity impact, high
- The undersized mapping causes out-of-bounds writes through drm_sysfb blit/disable paths and DRM/fbdev clients past the mapped firmware framebuffer, which is an OOB write scored as High integrity impact.
- A:HAvailability impact, high
- Accesses past the ioremap'd region cause kernel page-fault oops or panic during probe-time DRM client setup or later modeset/blit, fully denying availability on affected Open Firmware display systems.