CVE-2023-32233

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Last Modified: UTC

Important Important Impact What does this mean?
7.8 CVSS v3 Base Score

Description

A use-after-free vulnerability was found in the Netfilter subsystem of the Linux kernel when processing batch requests to update nf_tables configuration. This vulnerability can be abused to perform arbitrary reads and writes in kernel memory. A local user (with CAP_NET_ADMIN capability) could use this flaw to crash the system or potentially escalate their privileges on the system.

Statement

Only local users with CAP_NET_ADMIN capability (or root) can trigger this issue. On Red Hat Enterprise Linux, local unprivileged users can exploit unprivileged user namespaces (CONFIG_USER_NS) to grant themselves this capability.

The OpenShift Container Platform (OCP) control planes or master machines are based on Red Hat Enterprise Linux CoreOS (RHCOS) that consists primarily of RHEL components, hence is also affected by this kernel vulnerability. Like it is mentioned earlier, the successful exploit needs necessary privileges (CAP_NET_ADMIN) and direct, local access . Local user in RHCOS is already a root with full permissions, hence existence of this vulnerability does not bring any value from the potential attacker perspective. From the OpenShift containers perspective, this vulnerability cannot be exploited as in OpenShift the cluster processes on the node are namespaced, which means that switching in the running OpenShift container the namespace will not bring necessary capabilities. This means that for OpenShift, the impact of this vulnerability is Low. Similar to CVE-2023-32233 vulnerability has been explained in the following blog post as an example of "Container escape vulnerability": This content is not included.https://www.redhat.com/en/blog/containers-vulnerability-risk-assessment

Mitigation

1. This flaw can be mitigated by preventing the affected netfilter (nf_tables) kernel module from being loaded. For instructions on how to blacklist a kernel module, please see https://access.redhat.com/solutions/41278.

2. If the module cannot be disabled, on non-containerized deployments of Red Hat Enterprise Linux, the mitigation is to disable user namespaces:

# echo "user.max_user_namespaces=0" > /etc/sysctl.d/userns.conf
# sysctl -p /etc/sysctl.d/userns.conf
On containerized deployments, such as Red Hat OpenShift Container Platform, do not use the second mitigation (disabling user namespaces) as the functionality is needed to be enabled. The first mitigation (blacklisting nf_tables) is still viable for containerized deployments, providing the environment is not using netfilter.

Additional Information

External References

Content from www.cve.org is not included.https://www.cve.org/CVERecord?id=CVE-2023-32233

Content from nvd.nist.gov is not included.https://nvd.nist.gov/vuln/detail/CVE-2023-32233

Content from github.com is not included.https://github.com/torvalds/linux/commit/c1592a89942e9678f7d9c8030efa777c0d57edab

Content from www.openwall.com is not included.https://www.openwall.com/lists/oss-security/2023/05/08/4

Affected Packages and Issued Red Hat Security Errata

Products / Services Components State Errata
Red Hat Enterprise Linux 6 kernel Not affected
Red Hat Enterprise Linux 7 kpatch-patch Fixed RHSA-2023:5574
Red Hat Enterprise Linux 7 kernel-rt Fixed RHSA-2023:5621
Red Hat Enterprise Linux 7 kernel Fixed RHSA-2023:5622
Red Hat Enterprise Linux 7.4 Advanced Update Support kernel Fixed RHSA-2023:4699
Red Hat Enterprise Linux 7.6 Advanced Update Support(Disable again in 2026 - SPRHEL-7118) kernel Fixed RHSA-2023:4696
Red Hat Enterprise Linux 7.7 Advanced Update Support kernel Fixed RHSA-2023:5419
Red Hat Enterprise Linux 8 kernel Fixed RHSA-2023:3349
Red Hat Enterprise Linux 8 kernel-rt Fixed RHSA-2023:3350
Red Hat Enterprise Linux 8 kpatch-patch Fixed RHSA-2023:3351
Unless explicitly stated as not affected, all previous versions of packages in any minor update stream of a product listed here should be assumed vulnerable, although may not have been subject to full analysis.

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 Authorities (CNA) source for its products and services (see Red Hat classifications ).

CVSS v3 Score Breakdown Red Hat NVD
CVSS v3 Base Score 7.8 7.8
Attack Vector Local Local
Attack Complexity Low Low
Privileges Required Low Low
User Interaction None None
Scope Unchanged Unchanged
Confidentiality Impact High High
Integrity Impact High High
Availability Impact High High

CVSS v3 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

While PR:H is technically correct because of the CAP_NET_ADMIN capability requirement, unprivileged users on the system with unprivileged user namespaces enabled (this seems to be default among distributions) can grant themselves CAP_NET_ADMIN capability easily, so in practice, it's PR:L.

Acknowledgements

Red Hat would like to thank Patryk Sondej and Piotr Krysiuk for reporting this issue.

Frequently Asked Questions

Why is Red Hat's CVSS v3 score or Impact different from other vendors?

 For open source software shipped by multiple vendors, the CVSS base scores may vary for each vendor's version depending on the version they ship, how they ship it, the platform, and even how the software is compiled. This makes scoring of vulnerabilities difficult for third-party vulnerability databases such as NVD that only provide a single CVSS base score for each vulnerability. Red Hat scores reflect how a vulnerability affects our products specifically.

For more information, see https://access.redhat.com/solutions/762393.

My product is listed as "Under investigation" or "Affected", when will Red Hat release a fix for this vulnerability?
  • "Under investigation" doesn't necessarily mean that the product is affected by this vulnerability. It only means that our Analysis Team is still working on determining whether the product is affected and how it is affected.
  • "Affected" means that our Analysis Team has determined that this product is affected by this vulnerability and might release a fix to address this in the near future.

What can I do if my product is listed as "Will not fix"?

 A "will not fix" status means that a fix for an affected product version is not planned or not possible due to complexity, which may create additional risk.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Upgrade to a supported product version that includes a fix for this vulnerability (recommended).
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.

What can I do if my product is listed as "Fix deferred"?

 A deferred status means that a fix for an affected product version is not guaranteed due to higher-priority development work.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.
  • Red Hat Engineering focuses on addressing high-priority issues based on their complexity or limited lifecycle support. Therefore, lower-priority issues will not receive immediate fixes.

What is a mitigation?

 A mitigation is an action that can be taken to reduce the impact of a security vulnerability, without deploying any fixes.

I have a Red Hat product but it is not in the above list, is it affected?

 The listed products were found to include one or more of the components that this vulnerability affects. These products underwent a thorough evaluation to determine their affectedness by this vulnerability. Note that layered products (such as container-based offerings) that consume affected components from any of the products listed in this table may be affected and are not represented.

Why is my security scanner reporting my product as vulnerable to this vulnerability even though my product version is fixed or not affected?

 In order to maintain code stability and compatibility, Red Hat usually does not rebase packages to entirely new versions. Instead, we backport fixes and new features to an older version of the package we distribute. This can result in some security scanners that only consider the package version to report the package as vulnerable. To avoid this, we suggest that you use an approved vulnerability scanner from our This content is not included.Red Hat Vulnerability Scanner Certification program.