CVE-2021-33033
Description
A flaw use-after-free in the Linux kernel CIPSO network packet labeling protocol functionality was found in the way user open local network connection with the usage of the security labeling that is IP option number 134. A local user could use this flaw to crash the system or possibly escalate their privileges on the system.
Statement
Considered to be Moderate rate, because by default CIPSO non-enabled and both no known way to reproduce the attack remotely and both it looks complex if even possible to use the attack in any way apart from crashing the system. For the usage of the inbound CIPSO connections, the administrator have to enable it with netlabelctl utility first. The vulnerability is considered to be for local user, because it can happen only when a local user opens a socket for sending packets, but not during receiving packets.
Mitigation
The mitigation would be not allowing CIPSO labeling for the inbound network connections. For the most of the default configurations both for network routers and for the Linux servers itself it is disabled by default.
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 | 7.8 | 7.8 | 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 | 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:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Red Hat CVSS v3 Score Explanation
The CIA:H since considering use-after-free as memory write (because in this case theoretically possible to write memory after incorrect reading it).
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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