# CVE-2026-97604: fbdev: vfb: defer cleanup until the last reference

> A use-after-free in the Linux kernel's virtual framebuffer driver allows local attackers to execute code or escalate privileges via race conditions during device unbinding.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-104466, BELL-CVE-2026-97604, DEBIAN-CVE-2026-97604, GHSA-8fh7-qq2h-xhh6, UBUNTU-CVE-2026-97604

## What is CVE-2026-97604?

CVE-2026-97604 is an use after free vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

fbdev: vfb: defer cleanup until the last reference

FBIOGETCMAP takes a shallow snapshot of info->cmap and performs the
usercopy after dropping info->lock. vfb_remove() frees the colormap
immediately after unregistering the framebuffer, even when an open file
still holds a reference to fb_info. A concurrent driver unbind can
therefore free the colormap while the ioctl copies it to userspace.

KASAN reports:

  BUG: KASAN: slab-use-after-free in _copy_to_user
  Read of size 512 by task poc/125

   _copy_to_user (./include/linux/instrumented.h:129 ./include/linux/uaccess.h:201 lib/usercopy.c:24)
   fb_cmap_to_user (./include/linux/uaccess.h:230 drivers/video/fbdev/core/fbcmap.c:211)
   do_fb_ioctl (drivers/video/fbdev/core/fb_chrdev.c:114)

   Allocated by task 1:
   fb_alloc_cmap_gfp (./include/linux/slab.h:973 ./include/linux/slab.h:1290 drivers/video/fbdev/core/fbcmap.c:108)
   vfb_probe (drivers/video/fbdev/vfb.c:459)

   Freed by task 124:
   fb_dealloc_cmap (drivers/video/fbdev/core/fbcmap.c:151)
   vfb_remove (drivers/video/fbdev/vfb.c:489)

unregister_framebuffer() drops the registration reference, and fbdev calls
fb_destroy after the last put_fb_info(). Move the registered framebuffer's
cleanup into an fb_destroy callback so its colormap and screen buffer stay
alive until all file references have been released.

## Which versions are affected by CVE-2026-97604?


## How do I fix CVE-2026-97604?

Apply the vendor's patch.

## Is CVE-2026-97604 being exploited?

There is no known exploitation of CVE-2026-97604 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97604 and fix it if it is affected.

What it is: CVE-2026-97604 is an use after free vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-97604 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-97604/ (Markdown: https://insights.sbomify.com/CVE-2026-97604/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97604
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97604
- OSV: https://osv.dev/vulnerability/CVE-2026-97604

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97604/
Summaries are generated and may contain mistakes; the official description above is the record.