Security Bulletin: IBM i components are affected by CVE-2021-4104 (log4j version 1.x)

Summary

Multiple sub-components of IBM i ship log4j version v1.x files making them vulnerable to the issue described in the vulnerability details section. IBM Navigator for i - heritage version uses log4j v1.x and cannot be updated to log4j v2.x. Integrated Web Server (IWS) V2.6 contains unused references to log4j v1.x packages. IBM i 7.2 - Integrated Application Server (IAS) V7.1 & V8.1 and Integrated Web Server (IWS) V1.3 & V1.5 use log4j v1.x and cannot be updated to log4j v2.x. IBM i Access Client Solutions (ACS) version 1.1.8.6 and earlier included an unused log4j v1.x jar file. IBM i has addressed the applicable CVE as described in the Remediation/Fixes section.

Vulnerability Details

CVEID:CVE-2021-4104
**DESCRIPTION:**Apache Log4j could allow a remote attacker to execute arbitrary code on the system, caused by the deserialization of untrusted data when the attacker has write access to the Log4j configuration. If the deployed application is configured to use JMSAppender, an attacker could exploit this vulnerability to execute arbitrary code on the system.
CVSS Base score: 8.1
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/215048 for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H)

Affected Products and Versions

IBM i 7.4, 7.3, and 7.2 - V2.6

IBM i 7.2 - V1.3 and V1.5

Integrated Application Server (IAS)| IBM i 7.2 - V7.1 and V8.1
IBM i Access Client Solutions| 1.1.8.6 and earlier

Remediation/Fixes

IBM strongly recommends addressing the vulnerability now by applying the fixes.

IBM i Access Client Solutions version 1.1.8.6 and earlierincluded an unused log4j v1.x jar file. The issue can be fixed by upgrading to ACS version 1.1.8.7 or later. Details for how to get the latest version of IBM i Access Client Solutions are available at**<https://www.ibm.com/support/pages/ibm-i-access-client-solutions&gt;**

Integrated Web Server (IWS) V2.6 included unused references to log4j v1.x packages. The issue can be fixed by applying PTFs to IBM i. Releases 7.4 and 7.3 of IBM i will be fixed.

IBM i 7.2 only - Integrated Application Server (IAS) V7.1 & V8.1 and Integrated Web Services Server (IWS) V1.3 & V1.5 use log4j v1.x and cannot be updated. Customers can fix the log4j issues by migrating to the liberty-based support already available for ten years (V2.6). These server runtimes have been removed from the 7.2 release. With this fix, the server runtimes are removed and these servers will no longer run. If still using this level of IWS, migrate the web service to the V2.6 level before applying these PTFs. Details for migrating can be found at: <https://www.ibm.com/support/pages/how-migrate-your-ibm-integrated-web-services-iws-server-v13v15-v26&gt;. The issue can be fixed by applying PTFs to IBM i. Release 7.2 of IBM i will be fixed.

The IBM i PTF numbers containing the fixes follow. Future Group PTFs for HTTP Server will also contain the fixes for this CVE.

IBM i Release| 5770-DG1
IBM HTTP Server for i Group PTF - Level| PTF Download Link
—|—|—
7.4| SF99662 - 19| SF99662 740 IBM HTTP Server for i
7.3| SF99722 - 38| SF99722 730 IBM HTTP Server for i
7.2| SF99713 - 49| SF99713 720 IBM HTTP Server for i

<https://www.ibm.com/support/fixcentral&gt;

IBM Navigator for i - heritage versionuses log4j v1.x and cannot be updated to log4j v2.x or be removed from use. The issue can be resolved by permanently removing the heritage version of IBM Navigator for i from the partition.

The IBM i PTF numbers for removing the heritage version follow. Future Group PTFs for HTTP Server will NOT contain the fixes that remove the jar files for this CVE.

SI82995, SI82996

| <https://www.ibm.com/support/pages/ptf/SI82995&gt; <https://www.ibm.com/support/pages/ptf/SI82996&gt;
7.3| SI82997, SI82998| <https://www.ibm.com/support/pages/ptf/SI82997&gt; <https://www.ibm.com/support/pages/ptf/SI82998&gt;
7.2| SI83098, SI83099| <https://www.ibm.com/support/pages/ptf/SI83098&gt; <https://www.ibm.com/support/pages/ptf/SI83099&gt;

<https://www.ibm.com/support/fixcentral&gt;

Workarounds and Mitigations

IBM Navigator for i - heritage version uses log4j v1.x and cannot be updated to log4j v2.x or be removed from use.

The issue can be mitigated by discontinuing the use of the heritage version of IBM Navigator for i. The mitigation will remove the heritage version from the configuration of Admin2 and Admin2 will now start by default. Prior mitigation disabled the ADMIN2 server (where the heritage Navigator runs) from starting and running without user interaction. Additionally, the userdata runtime cache files (where the reference to log4j can be found) were deleted by this fix. The issue can be mitigated by applying PTFs to IBM i. Releases 7.4, 7.3, and 7.2 of IBM i will be mitigated.

It is strongly recommended that heritage Navigator be permanently removed by following the instructions in the remediation/fixes section, however if there are key features required, heritage Navigator can be enabled and started temporarily at your own risk. To do so, refer to these instructions: <https://www.ibm.com/support/pages/heritage-navigator-enable-and-disable-instructions&gt;

Note: If heritage Navigator is started, the userdata cache files are re-created and will have to be manually removed. Details are in the above link.

The IBM i PTF numbers containing the mitigation follow. Future Group PTFs for HTTP Server will also contain the mitigation for this CVE.

IBM i Release| 5770-DG1
IBM HTTP Server for i Group PTF - Level| PTF Download Link
—|—|—
7.4| SF99662 - 26| SF99662 740 IBM HTTP Server for i
7.3| SF99722 - 43| SF99722 730 IBM HTTP Server for i
7.2| SF99713 - 52| SF99713 720 IBM HTTP Server for i

<https://www.ibm.com/support/fixcentral&gt;