Month: December 2021

Urgent and Critical: Remote Code Execution in Apache Log4j needs immediate upgrade

viviandufour, , , , Leave a comment

Updated: 31 Dec 2021

5 minute read

This is a call to arms. All enterprise software maintainers of software using Java libraries need to check if their systems are affected by the newly discovered Apache Log4j vulnerability since its announcement on Dec 9, 2021. Since then several security vulnerabilities in the wild have been discovered.

CVE-2021-44832

Vulnerability Score: 6.6 (CVSS: 3.0 / AV: N / AC: L / PR: N / UI: N / S: C / C: H / I: H / A: H)
Platform: Java
Component: org.apache.logging.log4j:log4j-core
Affected versions: 2.0-alpha7 to 2.17.0 inclusive, except 2.3.2 and 2.12.4.
Fixed in version: 2.17.1

CVE-2021-44228

Vulnerability Score: 10.0 (CVSS: 3.0 / AV: N / AC: L / PR: N / UI: N / S: C / C: H / I: H / A: H)
Platform: Java
Component: org.apache.logging.log4j:log4j-core
Affected versions: all versions before 2.14.1, inclusive
Fixed in version: 2.15.0 but upgrade to 2.17.0 is required because of CVE-2021-45105

CVE-2021-45046

Vulnerability Score: 9.0 (AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H) (updated 18/12/2021)
Platform: Java
Component: org.apache.logging.log4j:log4j-core
Affected versions: all versions up to 2.15.0, excluding 2.12.2
Fixed in version: 2.16.0 but upgrade to 2.17.0 is required because of CVE-2021-45105

CVE-2021-45105

Vulnerability Score: 7.5 (CVSS: 3.0 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
Platform: Java
Component: org.apache.logging.log4j:log4j-core
Affected versions: all versions from 2.0-beta9 to 2.16.0, inclusive
Fixed in version: 2.17.0


Which systems does this affect?

Apache Log4j is probably the most common library used for logging in the Java ecosystem with over 400,000 downloads from its GitHub project. It is used in Java applications to log system and user activities, so there’s a serious possibility your Java software is using it. It is used, internally, by many other Apache frameworks such as Apache Flink, Apache Druid, Apache Flume, Apache Solr, Apache Flink, Apache Kafka, Apache Dubbo. It is also actively used in many other open source projects, like Redis, ElasticSearch, Elastic Logstash, Ghidra and many others.

Among all these open source components, one needs a special mention: Apache Struts. Yes, it is actively using Log4j. There exists a potential to trigger high-impact attacks against a wide variety of apps and services, similar to the scale witnessed in 2017. At that time, due to the vulnerability exploited in the Equifax megahack, 140 million customers’ data in North America and UK were breached. The latest version of Apache Struts, 2.5.28, uses by default Log4j version 2.12.21, which is vulnerable to this attack. This time, however, the scope for damage could be even wider, as Apache Struts is one of many Apache frameworks that use Log4j. 

The Java ecosystem is in very broad use in enterprise systems and web apps and many mainstream services are likely to be vulnerable. Therefore, software maintainers and developers should pay close attention to this vulnerability. 

This has been preliminary filed as CVE-2021-44228, and a subsequent vulnerability was also flagged, now filed under CVE-2021-45046.


Why does this threat demand an urgent patch?

This vulnerability allows the attacker to remotely execute code on your system, with the ability to gain complete control of the underlying servers.

This is actively exploited on the internet now and there is already a simple POC (proof of concept) available on the internet that explains how to do it. 

From https://www.wired.com/story/log4j-flaw-hacking-internet/:

“All an attacker has to do to exploit the flaw is strategically send a malicious code string that eventually gets logged by Log4j version 2.0 or higher. The exploit lets an attacker load arbitrary Java code on a server, allowing them to take control.  […]Minecraft screenshots circulating on forums appear to show players exploiting the vulnerability from the Minecraft chat function. On Friday, some Twitter users began changing their display names to code strings that could trigger the exploit. Another user changed his iPhone name to do the same and submitted the finding to Apple. Researchers told WIRED that the approach could also potentially work using email.”

If you maintain an enterprise system using Java software, you would need to update all affected applications, whether they are maintained directly by your organisation or your supplier organisation.

Within 2 days of the 2017 vulnerability being announced, several systems around the world were breached by exploiting the software weakness.  We do not want more cyber breaches of such scale and all need to react quickly to patch vulnerable systems.


How can I check if my system is affected?

If you maintain any software using Java libraries, check if you are using Apache Log4j.  Meterian BOSS scanner can be used to scan your codebase to identify all dependent software libraries.  If it is using Log4j, it will find the affected vulnerable versions and provide more information on how to mitigate this risk.

If you are a developer and you have access to the code, you can simply execute this command from your terminal:

$ mvn dependency:tree | grep log4j-core | grep compile
[INFO] +- org.apache.logging.log4j:log4j-core:jar:2.12.1:compile

If you see any response lines, check the version: if it’s below 2.16.0 (as in the above example) you may be affected.


My system has the vulnerable log4j library — how can I mitigate the risk?

There is a patched version of the library that resolves the issue.  Released by Apache Software Foundation, the solution is to immediately upgrade log4j to the latest log4j version 2.16.0.  The fixed version is available via Maven. 

If the library is coming from a transitive dependency (it’s not one of your direct dependencies, but a dependency of them) you can just include an override in your root pom.xml (or where applicable) and retest that it’s not there anymore with the command shown before:

    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-core</artifactId>
        <version>2.16.0</version>
    </dependency>

A set of mitigations, specific to the version you are using, are also available on the Apache Log4j website. The Apache Struts team provided specific advice on how to handle the issue.

If you are using an external product that runs with Java, you can also protect your systems by launching the JVM with this special parameter:

-Dlog4j2.formatMsgNoLookups=true

This is useful for tools like Jenkins, where you have control of the installation but you do not have control of the code, but please note that this does not protect against the latest CVE.


What can I do to proactively protect from such vulnerabilities?

We always suggest you regularly scan your software code bases. 


Are Meterian applications affected by the log4j vulnerability?

No. We have verified our applications and none are using log4j.  We maintain a continuous monitoring system to ensure our development operations are up to date with the latest known vulnerabilities in software components.   

Related references

Urgent and Critical: Remote Code Execution in Apache Log4j needs immediate upgrade