CVE-2021-22600
Description
A double-free flaw was found in the Linux kernel’s packet protocol subsystem in the way a user call triggers the packet_set_ring() function of the net/packet/af_packet.c. This flaw allows a local user to crash or escalate their privileges on the system.
Statement
The Red Hat Enterprise Linux versions before 9 are not affected, because the commit that introduced the bug is not in currently supported versions of Red Hat Enterprise Linux. The commit that introduced this bug is: 61fad6816fc1 ("net/packet: tpacket_rcv: avoid a producer race condition").
Mitigation
Only users with access to the AF_PACKET socket can trigger this vulnerability. The mitigation would be to disable CAP_NET_RAW capability for the users that prevents access to AF_PACKET.
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 | 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 AC:H is similar to the other previous CVE-2017-7308 that both affects packet_set_ring() function (more information about CVE-2017-7308 could be found in this blog: https://googleprojectzero.blogspot.com/2017/05/exploiting-linux-kernel-via-packet.html ).
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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