CVE-2026-93121 Linux CVE debrief

Who should care

Linux kernel maintainers, users, and administrators should assess exposure and verify patch deployment to prevent potential issues. This includes affected operators, platform administrators, vulnerability management teams, and security teams who need to evaluate the impact on their systems and take appropriate actions.

Why it matters

CVE-2026-93121 is a vulnerability in the Linux kernel's USB gadget function f_fs that requires verification of patch deployment to prevent undefined behavior. Linux kernel maintainers and users should assess exposure.

• Verification of patch deployment is necessary to prevent undefined behavior in the Linux kernel's USB gadget function f_fs.
• Linux kernel maintainers and users need to assess exposure to this vulnerability.
• The vulnerability's impact requires verification from official sources due to limited information.

Technical summary

The ffs_dmabuf_transfer() function in the Linux kernel's USB gadget function f_fs has a vulnerability. In error paths for endpoint-disabled and request-allocation failure conditions, dma_fence_put() is called on a fence that has only been kmalloc'd and not fully initialized with dma_fence_init(). This leads to undefined behavior. The correct action is to use kfree() for cleanup at that stage, and the label should be renamed to err_fence_free to reflect the actual cleanup action.

Defensive priority

Linux kernel maintainers and users should assess exposure and verify patch deployment.

Recommended defensive actions

• Review Linux kernel versions and configurations for exposure.
• Verify deployment of the patch for f_fs in the USB gadget function.
• Monitor for updates from the Linux kernel maintainers.
• Perform compensating controls review for exposed systems.
• Check relevant monitoring, detection, and logs for exposed assets.
• Track exceptions and retest remediated assets.
• Plan vendor-supported updates or mitigations through normal change control.

Evidence notes

The CVE record and NVD entry provide details on the vulnerability. Four source references from the Linux kernel Git repository are available. The vulnerability affects Linux kernel versions and requires verification of patch deployment to prevent undefined behavior in the USB gadget function f_fs. Linux kernel maintainers and users should assess exposure and verify patch deployment. The error paths for endpoint-disabled and request-allocation failure conditions call dma_fence_put() on a fence that has only been kmalloc'd and not fully

Sources and references

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.