CVE-2026-99155
Description
A flaw was found in the Linux kernel's Xen virtual Small Computer System Interface (SCSI) frontend driver. This vulnerability allows a malicious or compromised backend service to trigger a Denial of Service (DoS) by crashing the guest virtual machine. The issue occurs when the driver processes a storage response referencing an inactive request identifier, causing the system to dereference an unpopulated pointer due to missing validation.
Statement
This vulnerability is classified as having Moderate severity because exploitation requires elevated host privileges or a compromised Xen backend domain, restricting exposure exclusively to Xen-virtualized guests using virtual SCSI devices. In standard Red Hat Enterprise Linux environments, virtualization primarily utilizes KVM with virtio storage rather than Xen paravirtualized SCSI drivers. Furthermore, triggering the unpopulated pointer dereference results only in a guest denial of service without permitting arbitrary code execution or data leakage.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.4 | N/A | N/A |
| Attack Vector | Local | N/A | N/A |
| Attack Complexity | Low | N/A | N/A |
| Privileges Required | High | N/A | N/A |
| User Interaction | None | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | None | N/A | N/A |
| Integrity Impact | None | N/A | N/A |
| Availability Impact | High | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart
NULL pointer dereferences usually result in the failure of the process unless exception handling (on some platforms) is available and implemented. Even when exception handling is being used, it can still be very difficult to return the software to a safe state of operation.
Integrity,Confidentiality
Technical Impact: Execute Unauthorized Code or Commands; Read Memory; Modify Memory
In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.
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