CVE-2019-11811
Description
A flaw was found in the Linux kernel's implementation of IPMI (remote baseband access). An attacker, with local access to read /proc/ioports, may be able to create a use-after-free condition when the kernel module is unloaded which may result in privilege escalation.
Statement
This flaw has been rated as "Moderate" as the attacker needs to be able to abuse this flaw in a very narrow race condition of the kernel module being unloaded. This scoring system from this flaw differentiates from other sources as the attacker must have a local account to be able to read the file (/proc/ioports) while the module is unloaded. None of the above actions are 'network facing' attack vectors.
Mitigation
A mitigation to this flaw would be to no longer use IPMI on affected hardware until the kernel has been updated. Existing systems that have IPMI kernel modules loaded will need to unload the "ipmi_si" kernel module and blacklist ( See https://access.redhat.com/solutions/41278 for a guide on how to blacklist modules). Take careful consideration that if unloading and blacklisting the module, this creates a one-time attack vector window for a local attacker.
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 | 7 | 7 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | High | High | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | 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:3.1/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:L/UI:N/S:U/C:H/I:H/A:H
Red Hat CVSS v3 Score Explanation
The attacker needs to be able to abuse this flaw in a very narrow race condition (AC:H) of the kernel module being unloaded. This scoring system from this flaw differentiates from other sources as the attacker must have a local account (AV:L) to be able to read the file (/proc/ioports) while the module is unloaded. None of the above actions are 'network facing' attack vectors.
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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