CVE-2026-63899 Linux CVE debrief

Who should care

Users of Linux kernel with USB: serial: mxuport functionality, Linux kernel maintainers, and security teams responsible for vulnerability management should be aware of this vulnerability. They should review the official advisory and apply the patch or implement mitigations as necessary.

Technical summary

The Linux kernel has a vulnerability in the USB: serial: mxuport functionality. The vulnerability could allow user-controlled slab corruption if a malicious device reports a smaller size. The fix ensures that the bulk-out endpoint max packet size is at least eight bytes to prevent the corruption. Users of the Linux kernel with USB: serial: mxuport functionality should verify and apply the kernel patch, monitor for malicious devices, and implement compensating controls.

Defensive priority

Medium

Recommended defensive actions

• Verify and apply the kernel patch
• Monitor for malicious devices
• Implement compensating controls
• Review the official advisory
• Perform vulnerability scanning
• Inventory affected systems
• Track patch deployment

Evidence notes

The CVE record was published on 2026-07-19T16:17:07.497Z and has not been modified since then. The NVD entry is currently Received. There is limited information available about the vulnerability, and defenders should verify the affected scope and severity with the official advisory. The vulnerability affects the Linux kernel's USB: serial: mxuport functionality. The fix ensures that the bulk-out endpoint max packet size is at least eight bytes to avoid user-controlled slab corruption. Evidence is limited to CVE and NVD details.

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.