CVE-2021-0920
Description
A vulnerability was found in unix_dgram_recvmsg in net/unix/af_unix.c in the Linux kernel's garbage collection for Unix domain socket file handlers. In this flaw, a missing cleanup may lead to a use-after-free due to a race problem. This flaw allows a local user to crash the system or escalate their privileges on the system.
A read-after-free memory flaw was found in the Linux kernel's garbage collection for Unix domain socket file handlers in the way users call close() and fget() simultaneously and can potentially trigger a race condition. This flaw allows a local user to crash the system or escalate their privileges on the system.
Mitigation
Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
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 | 7.4 | 6.4 | 6.4 |
| Attack Vector | Local | Local | Local |
| Attack Complexity | High | High | High |
| Privileges Required | None | High | High |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | High | High | High |
| Integrity Impact | High | High | High |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
Red Hat CVSS v3 Score Explanation
This flaw depends on another flaw: CVE-2021-4083
kernel: fget: check that the fd still exists after getting a ref to it
which is exploitable without any privilege (PR:N) required.
This is an interlinked flaw, and need both patches to fix this complete problem combined.
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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