CVE-2021-22555

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Last Modified: UTC

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

Description

A flaw was discovered in processing setsockopt IPT_SO_SET_REPLACE (or IP6T_SO_SET_REPLACE) for 32 bit processes on 64 bit systems. This flaw will allow local user to gain privileges or cause a DoS through user name space. This action is usually restricted to root-privileged users but can also be leveraged if the kernel is compiled with CONFIG_USER_NS and CONFIG_NET_NS and the user is granted elevated privileges.

Statement

In Red Hat Enterprise Linux 7, only privileged users can trigger this bug. In Red Hat Enterprise Linux 8 a regular user can trigger it, however the result is corruption of 4 bytes of memory.

Mitigation

The mitigation for the Red Hat Enterprise Linux 8 is to disable unprivileged users from running unshare(CLONE_NEWUSER) or unshare(CLONE_NEWNET) that could be done with this command:
echo 0 > /proc/sys/user/max_user_namespaces

For making this change in configuration permanent.
Note: User namespaces are used primarily for Linux containers. If containers are in use, this requirement is not applicable.
Configure RHEL 8 to disable the use of user namespaces by adding the following line to a file in the "/etc/sysctl.d/" directory:

user.max_user_namespaces = 0

The system configuration files need to be reloaded for the changes to take effect. To reload the contents of the files, run the following command:

$ sudo sysctl --system

The other mitigation for containers, if without disabling user namespaces, is blocking the pertinent syscalls in a seccomp policy file. For more information about seccomp, please read: This content is not included.https://www.openshift.com/blog/seccomp-for-fun-and-profit

Additional Information

External References

Content from www.cve.org is not included.https://www.cve.org/CVERecord?id=CVE-2021-22555

Content from nvd.nist.gov is not included.https://nvd.nist.gov/vuln/detail/CVE-2021-22555

Content from git.kernel.org is not included.https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=b29c457a6511435960115c0f548c4360d5f4801d

Content from github.com is not included.https://github.com/google/security-research/security/advisories/GHSA-xxx5-8mvq-3528

Content from www.cisa.gov is not included.https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Affected Packages and Issued Red Hat Security Errata

Products / Services Components State Errata
Red Hat Enterprise Linux 6 Extended Lifecycle Support - EXTENSION kernel Fixed RHSA-2025:17733
Red Hat Enterprise Linux 7 kernel Fixed RHSA-2021:3327
Red Hat Enterprise Linux 7 kernel-rt Fixed RHSA-2021:3328
Red Hat Enterprise Linux 7 kpatch-patch Fixed RHSA-2021:3381
Red Hat Enterprise Linux 7 kernel-alt Out of support scope
Red Hat Enterprise Linux 7.2 Advanced Update Support kernel Fixed RHSA-2021:3399
Red Hat Enterprise Linux 7.3 Advanced Update Support kernel Fixed RHSA-2021:3321
Red Hat Enterprise Linux 7.4 Advanced Update Support kernel Fixed RHSA-2021:3725
Red Hat Enterprise Linux 7.6 Advanced Update Support(Disable again in 2026 - SPRHEL-7118) kernel Fixed RHSA-2021:3812
Red Hat Enterprise Linux 7.6 Telco Extended Update Support kernel Fixed RHSA-2021:3812
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

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.