CVE-2015-8963
Description
Race condition in kernel/events/core.c in the Linux kernel before 4.4 allows local users to gain privileges or cause a denial of service via use-after-free vulnerability by leveraging incorrect handling of an swevent data structure during a CPU unplug operation.
Statement
This issue affects the Linux kernel shipping with Red Hat Enterprise Linux 6. Future updates for the respective releases may address the issue.
This issue does not not affect Red Hat Enterprise Linux 5, 7, MRG-2 kernels.
This has been rated as having Moderate security impact and is not currently planned to be addressed in future updates of Red Hat Enterprise Linux 5. For additional information, refer to the Red Hat Enterprise Linux Life Cycle: https://access.redhat.com/support/policy/updates/errata/.
Mitigation
A possible mitigation is to only remove CPU's while the system is shut down. This will prevent local attackers from being able to abuse this flaw.
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 | 7 | 7 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | High | High | N/A |
| Privileges Required | Low | None | N/A |
| User Interaction | None | Required | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | High | High | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory
The use of previously freed memory may corrupt valid data, if the memory area in question has been allocated and used properly elsewhere.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If chunk consolidation occurs after the use of previously freed data, the process may crash when invalid data is used as chunk information.
Confidentiality
Technical Impact: Read Memory
Read operations on freed memory can sometimes leak sensitive information instead of causing a crash
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If malicious data is entered before chunk consolidation can take place, it may be possible to take advantage of a write-what-where primitive to execute arbitrary code. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.
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