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CVE-2026-46065 Linux CVE debrief

A use-after-free vulnerability in the Linux kernel's framebuffer deferred I/O (fbdev/defio) subsystem has been resolved. The issue occurred when a graphics device was hot-unplugged while user space maintained an active memory mapping of the framebuffer. The hot-unplug operation freed the struct fb_info instance, but subsequent accesses through the still-active mapping operated on undefined memory state, leading to potential kernel memory corruption or information disclosure. The fix decouples deferred I/O state from struct fb_info lifetime by introducing struct fb_deferred_io_state, which persists until all mappings are closed. If fb_info is freed first, the state is invalidated and further accesses generate SIGBUS rather than dereferencing freed memory.

Vendor
Linux
Product
Unknown
CVSS
Unknown
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-27
Original CVE updated
2026-05-27
Advisory published
2026-05-27
Advisory updated
2026-05-27

Who should care

Linux system administrators running graphical workloads on systems with hot-pluggable graphics hardware; embedded developers using fbdev for display output; security teams monitoring for kernel memory safety issues in graphics subsystems

Technical summary

The Linux kernel's framebuffer deferred I/O mechanism previously stored state directly in struct fb_info, which could be freed during device hot-unplug while user space mappings remained active. The fix introduces struct fb_deferred_io_state as a separate allocation with independent lifetime, clearing its fb_info pointer when the framebuffer is released. This ensures that access through stale mappings results in SIGBUS delivery to user space rather than kernel use-after-free. The vulnerability affects systems using fbdev with deferred I/O where graphics devices may be hot-unplugged.

Defensive priority

high

Recommended defensive actions

  • Apply kernel updates containing the referenced stable tree commits for affected kernel versions
  • Audit systems using framebuffer devices with deferred I/O (fbdev/defio) for hot-plug scenarios
  • Monitor for SIGBUS signals in graphics applications as potential indicators of attempted exploitation
  • Review custom framebuffer drivers for similar lifetime management issues

Evidence notes

The vulnerability description and resolution are sourced from the official CVE record published 2026-05-27. Multiple kernel.org stable tree commits are referenced, indicating backports to maintained kernel branches. The fix addresses a long-standing architectural issue in fbdev deferred I/O lifetime management.

Official resources

2026-05-27