PatchSiren

PatchSiren cyber security CVE debrief

CVE-2026-46220 Linux CVE debrief

A local denial-of-service vulnerability exists in the Linux kernel's AMDGPU SDMA4 driver. The `sdma_v4_0_ring_emit_fence()` function contained `BUG_ON()` assertions verifying dword alignment of fence writeback addresses. These assertions were reachable from unprivileged userspace through crafted `DRM_IOCTL_AMDGPU_CS` submissions, causing fatal kernel panics in scheduler worker threads. The fix replaces both `BUG_ON()` calls with `WARN_ON()` to log the condition without crashing the kernel. The vulnerability was disclosed on 2026-05-28.

Vendor
Linux
Product
Unknown
CVSS
MEDIUM 5.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-28
Original CVE updated
2026-06-10
Advisory published
2026-05-28
Advisory updated
2026-06-10

Who should care

Linux system administrators running kernels with AMDGPU support; organizations using AMD GPUs in desktop, workstation, or server environments; security teams monitoring for local privilege escalation or denial-of-service vectors in graphics drivers

Technical summary

The AMDGPU SDMA4 driver's fence emission routine used `BUG_ON()` assertions to validate dword-aligned fence writeback addresses. These assertions were reachable from unprivileged userspace through the `DRM_IOCTL_AMDGPU_CS` IOCTL, allowing local attackers to trigger kernel panics. The vulnerability represents a defense-in-depth failure where kernel crash assertions were exposed to untrusted input rather than being restricted to internal driver invariants. The fix converts fatal assertions to warnings, deferring proper input validation to the CS IOCTL entry point.

Defensive priority

medium

Recommended defensive actions

  • Apply kernel updates containing the referenced stable branch commits when available from your Linux distribution
  • Monitor vendor security advisories for backported fixes to currently deployed kernel versions
  • Consider restricting unprivileged access to AMDGPU DRM devices where feasible as a temporary mitigation
  • Review system logs for WARN_ON messages indicating misaligned fence addresses that may indicate driver bugs

Evidence notes

The CVE description and kernel commit references confirm the vulnerability: unprivileged userspace could trigger `BUG_ON(addr & 0x3)` assertions in `sdma_v4_0_ring_emit_fence()` via the AMDGPU CS IOCTL path, resulting in kernel panic. The fix (cherry-picked from commit b90250bd933afd1ba94d86d6b13821997b22b18e) replaces fatal assertions with non-fatal warnings. Multiple stable kernel branch commits are referenced indicating backports to affected versions.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-46220 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-46220

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

  • CVE-2026-46220 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-46220

    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/0b91ea46bb68abf98a082bf239092253bbd6aaa2

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

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/4f7ca00fa91daf0795ec6b3b130c5ebba1f155fe

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

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/78d2e624fa073c14970aa097adcf3ea31c157a66

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

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/a4fd82fb0757c180bf622907397c528b89a827b2

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

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/d331fb241a4602253976ddd65144a8ba2b05665d

    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.