CVE-2023-52463
Description
A flaw was found in the Linux kernel, which involves the improper handling of the efivarfs filesystem when the firmware does not support the SetVariable function at runtime. Specifically, even if efivarfs is initially mounted as read-only (RO), it can be remounted as read-write (RW) without checking if the firmware can handle variable updates. This issue allows operations such as efi-updatevar to be executed, which leads to a crash due to a NULL pointer dereference. This crash occurs because the callback for SetVariable is not assigned, causing a level 0 translation fault.
Statement
This vulnerability is classified as Moderate severity because it requires specific conditions to be exploited: the system must be using a firmware that does not support the SetVariable function at runtime, and an attacker must have the ability to remount the efivarfs filesystem with read-write permissions. While it does not provide direct unauthorized access or code execution, the resulting crash from a NULL pointer dereference can cause denial of service, disrupting normal system operations. The impact is limited to systems with the specified firmware and does not affect systems where the SetVariable function is properly supported, reducing the overall exposure and potential damage.
Mitigation
No mitigation is currently available for this vulnerability. Make sure to perform the updates as they become available.
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).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | 5.5 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:L/AC:L/PR:L/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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