CVE-2022-20368
Description
An out-of-bounds access issue was found in the Linux kernel networking subsystem in the way raw packet sockets (AF_PACKET) used PACKET_COPY_THRESH and mmap operations. A local attacker with CAP_NET_RAW capability could use this flaw to trigger a buffer overflow resulting in a system crash or privilege escalation.
Statement
Only local users with CAP_NET_RAW capability enabled can trigger this issue. On Red Hat Enterprise Linux 8 CAP_NET_RAW capability can be gained by exploiting unprivileged user namespaces.
In a default or common use of Red Hat Enterprise Linux 7 unprivileged user namespaces are disabled by default, so local unprivileged users cannot abuse namespaces to grant themselves the CAP_NET_RAW capability and potentially elevate their privileges on the system.
Mitigation
The mitigation is to disable CAP_NET_RAW capability for regular users and executables to prevent access to raw packet sockets (AF_PACKET). On Red Hat Enterprise Linux 8, the mitigation is to either disable unprivileged user namespaces with `sysctl -w user.max_user_namespaces=0` or network namespaces with `sysctl -w user.max_net_namespaces=0`. For more information on how to set sysctl variables on Red Hat Enterprise Linux, please refer to https://access.redhat.com/solutions/2587.
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 | 7.8 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | High | 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:H/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
While PR:H is technically correct because of the CAP_NET_RAW capability requirement, unprivileged users on the system with unprivileged user namespaces enabled (this seems to be default among distributions) can grant themselves CAP_NET_RAW capability easily, so in practice, it's PR:L.
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Write operations could cause memory corruption. In some cases, an adversary can modify control data such as return addresses in order to execute unexpected code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
Attempting to access out-of-range, invalid, or unauthorized memory could cause the product to crash.
Other
Technical Impact: Unexpected State
Subsequent write operations can produce undefined or unexpected results.
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