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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
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-27
Original CVE updated
2026-06-24
Advisory published
2026-05-27
Advisory updated
2026-06-24

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.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-46065 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-46065

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-46065 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-46065

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/25c2b77bc463f29ee71a54b883548baf9386a0db

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/2a40f8bc9bb713329f1c35ffc199ee961a7135b0

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/2b53d3a52e8e5403a4f4fb57ac6cad3fd2cb1066

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/9ded47ad003f09a94b6a710b5c47f4aa5ceb7429

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/a0aafb421dd15e935d81543152617f2742cefa70

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.