CVE-2021-4104

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Moderate Moderate Impact What does this mean?
7.5 CVSS v3 Base Score

Description

A flaw was found in the Java logging library Apache Log4j in version 1.x. JMSAppender in Log4j 1.x is vulnerable to deserialization of untrusted data. This allows a remote attacker to execute code on the server if the deployed application is configured to use JMSAppender and to the attacker's JNDI LDAP endpoint.

Statement

Based on the conditions to be exploitable (see details below), the risk is much lower than Log4j 2.x and Red Hat has assessed this to be Moderate severity. This flaw has been filed for Log4j 1.x, and the corresponding flaw information for Log4j 2.x is available at: https://access.redhat.com/security/cve/CVE-2021-44228

Note this flaw ONLY affects applications which are specifically configured to use JMSAppender, which is not the default, or when the attacker has write access to the Log4j configuration for adding JMSAppender to the attacker's JNDI LDAP endpoint.

If the Log4j configuration is set TopicBindingName or TopicConnectionFactoryBindingName configurations allowing JMSAppender to perform JNDI requests that result in remote code execution in a similar fashion to CVE-2021-44228 Log4j 2.x, Log4j 1.x is vulnerable. However, the attack vector is reduced as it depends on having write access, which is not a standard configuration rather than untrusted user input. These are sufficient factors beyond the attacker's control.

The tomcat package shipped with Red Hat Enterprise Linux does not include log4j but it does include a default configuration for log4j, log4j.properties, which could be used with tomcat if users choose to install and configure the library. The JMSAppender is not enabled by default, and the permissions of the file can only be modified as root.

Red Hat Virtualization ships log4j12-1.2.17, but it is used and configured in a way which makes this flaw not possible to exploit. Therefore impact is rated Low.

Mitigation

These are the possible mitigations for this flaw for releases version 1.x:

- Comment out or remove JMSAppender in the Log4j configuration if it is used
- Remove the JMSAppender class from the classpath. For example:

zip -q -d log4j-*.jar org/apache/log4j/net/JMSAppender.class
- Restrict access for the OS user on the platform running the application to prevent modifying the Log4j configuration by the attacker.

Additional Information

External References

Content from www.cve.org is not included.https://www.cve.org/CVERecord?id=CVE-2021-4104

Content from nvd.nist.gov is not included.https://nvd.nist.gov/vuln/detail/CVE-2021-4104

Content from github.com is not included.https://github.com/apache/logging-log4j2/pull/608#issuecomment-990494126

Content from github.com is not included.https://github.com/apache/logging-log4j2/pull/608#issuecomment-991723301

Content from lists.apache.org is not included.https://lists.apache.org/thread/0x4zvtq92yggdgvwfgsftqrj4xx5w0nx

Content from www.openwall.com is not included.https://www.openwall.com/lists/oss-security/2021/12/13/1

Affected Packages and Issued Red Hat Security Errata

Products / Services Components State Errata
A-MQ Clients 2 log4j Affected
EAP 6.4 log4j async log4j Fixed RHSA-2022:0437
EAP 6.4.24 release Fixed RHSA-2022:5458
RHEL-8 based Middleware Containers rh-sso-7/sso74-openshift-rhel8 Fixed RHSA-2022:0444
RHEL-8 based Middleware Containers rh-sso-7/sso74-openj9-openshift-rhel8 Fixed RHSA-2022:0445
RHEL-8 based Middleware Containers rh-sso-7/sso7-rhel8-operator-bundle Fixed RHSA-2022:0450
RHEL-8 based Middleware Containers rh-sso-7/sso75-openshift-rhel8 Fixed RHSA-2022:0450
RHSSO 7.5.1 log4j Fixed RHSA-2022:0449
Red Hat AMQ Broker 7 log4j Affected
Red Hat Data Grid 7.3.9 log4j Fixed RHSA-2022:0430
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 7.5 7.5
Attack Vector Network Network
Attack Complexity High High
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:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

NVD CVSS:3.1/AV:N/AC:H/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.

My product is listed as "Out of Support Scope". What does this mean?

 When a product is listed as "Out of Support Scope", it means a vulnerability with the impact level assigned to this CVE is no longer covered by its current support lifecycle phase. The product has been identified to contain the impacted component, but analysis to determine whether it is affected or not by this vulnerability was not performed. The product should be assumed to be affected. Customers are advised to apply any mitigation options documented on this page, consider removing or disabling the impacted component, or upgrade to a supported version of the product that has an update available.