CVE-2026-98755

What it actually does

The vulnerability allows leakage of uninitialized kernel stack memory via the tag.stype_env field of a partially initialized vio_vcc struct that is sent through ldc_write() in vcc_send_ctl().

Why it matters to the business

Attackers may obtain fragments of sensitive kernel memory contents that could contain credentials or internal state useful for further attacks, increasing risk in virtualized or multi-tenant Linux environments.

How an attack unfolds

An attacker acting as an LDC peer triggers or observes vcc_send_ctl() calls; the uninitialized field in the stack-allocated packet carries residual kernel stack bytes that are transmitted and can be inspected for useful data.

How to fix it

Apply the upstream kernel commit that zero-initializes the vio_vcc pkt struct before ldc_write(); rebuild or update to a kernel containing the fix.

How to confirm the fix worked

Confirm the zero-initialization change is present in the vcc_send_ctl() function of the running kernel source or verify updated kernel packages have been installed and rebooted.

Typical attack path

1. Gain position as an LDC peer in the same domain or hypervisor setup
2. Induce or wait for vcc_send_ctl() execution paths
3. Receive the control packet via ldc_write()
4. Extract and analyze the uninitialized tag.stype_env bytes for kernel data

How to detect it

Inspect LDC packet captures or kernel logs around vcc_send_ctl() calls for anomalous or non-zero tag fields; post-exploitation detection is difficult without memory forensics or traffic analysis.

What your security team should do

• Prioritize kernel updates for affected Linux systems within standard patch windows
• Review and restrict LDC peer configurations where possible
• Monitor EPSS and exploit maturity indicators for any future increase