CVE-2021-4197
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Description
An unprivileged write to the file handler flaw in the Linux kernel's control groups and namespaces subsystem was found in the way users have access to some less privileged process that are controlled by cgroups and have higher privileged parent process. It is actually both for cgroup2 and cgroup1 versions of control groups. A local user could use this flaw to crash the system or escalate their privileges on the system.
Mitigation
The mitigation not known. However, for the default configuration of the Red Hat Enterprise Linux it is not possible to trigger this vulnerability: if control groups (cgroups) not being used or being used with the default configuration or being used some other configuration where for example similar privileges for all processes (both for parent and for child processes), then no way to trigger this vulnerability.
Additional information
- Bugzilla 2035652: kernel: cgroup: Use open-time creds and namespace for migration perm checks
- CWE-287: Improper Authentication
- FAQ: Frequently asked questions about CVE-2021-4197
Common Vulnerability Scoring System (CVSS) Score Details
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).
| Red Hat | NVD | |
|---|---|---|
CVSS v3 Base Score | 6.3 | 7.8 |
Attack Vector | Local | Local |
Attack Complexity | High | Low |
Privileges Required | Low | Low |
User Interaction | None | None |
Scope | Unchanged | Unchanged |
Confidentiality Impact | High | High |
Integrity Impact | High | High |
Availability Impact | None | High |
CVSS v3 Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
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 described problem with cgroups doesn't allow to trigger the attack with default configuration, but requires both non default configuration and some additional conditions to happen together, so hard to trigger (AC:H).
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability,Access Control
Technical Impact: Read Application Data; Gain Privileges or Assume Identity; Execute Unauthorized Code or Commands
This weakness can lead to the exposure of resources or functionality to unintended actors, possibly providing attackers with sensitive information or even execute arbitrary code.
Frequently Asked Questions
Why is Red Hat's CVSS v3 score or Impact different from other vendors?
My product is listed as "Under investigation" or "Affected", when will Red Hat release a fix for this vulnerability?
What can I do if my product is listed as "Will not fix"?
What can I do if my product is listed as "Fix deferred"?
What is a mitigation?
I have a Red Hat product but it is not in the above list, is it affected?
Why is my security scanner reporting my product as vulnerable to this vulnerability even though my product version is fixed or not affected?
My product is listed as "Out of Support Scope". What does this mean?
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