CVE-2021-44228: Proof-of-Concept for Critical Apache Log4j Remote Code Execution Vulnerability Available (Log4Shell)

CVE-2021-44228: Proof-of-Concept for Critical Apache Log4j Remote Code Execution Vulnerability Available (Log4Shell)

Critical vulnerability in the popular logging library, Log4j 2, impacts a number of services and applications, including Minecraft, Steam and Apple iCloud. Attackers have begun actively scanning for and attempting to exploit the flaw.

Update December 11: The Identifying Affected Systems section has been updated to reflect the availability of Tenable.io, Tenable.sc and Nessus Professional scan templates and Tenable.sc/Tenable.io dashboard and new widgets for Tenable.io.

On December 9, researchers published proof-of-concept (PoC) exploit code for a critical vulnerability in Apache Log4j 2, a Java logging library used by a number of applications and services including but not limited to:

Dubbed Log4Shell by researchers, the origin of this vulnerability began with reports that several versions of Minecraft, the popular sandbox video game, were affected by this vulnerability.

there’s a minecraft client & server exploit open right now which abuses a vulerability in log4j versions 2.0 – 2.14.1, there are proofs of concept going around already.

— ᵃᵈᵃᵐ (@twokilohertz)

Additionally, it appears that cloud services such as Steam and Apple iCloud are also affected.

This vulnerability is considered so severe that Cloudflare CEO plans to offer protections for all customers.

CVE-2021-44228 is a remote code execution (RCE) vulnerability in Apache Log4j 2. An unauthenticated, remote attacker could exploit this flaw by sending a specially crafted request to a server running a vulnerable version of log4j. The crafted request uses a Java Naming and Directory Interface (JNDI) injection via a variety of services including:

If the vulnerable server uses log4j to log requests, the exploit will then request a malicious payload over JNDI through one of the services above from an attacker-controlled server. Successful exploitation could lead to RCE.

In the case of Minecraft, users were able to exploit this vulnerability by sending a specially crafted message through Minecraft chat.

aaaaand then code execution?? #log4j #minecraft pic.twitter.com/aSFzhsm87l

— John Hammond (@_JohnHammond)

Both GreyNoise and Bad Packets have detected mass scanning activity searching for servers using Log4j.

Mass scanning activity detected from multiple hosts checking for servers using Apache Log4j (Java logging library) vulnerable to remote code execution (https://t.co/GgksMUlf94).

Query our API for “tags=CVE-2021-44228” for source IP addresses and other IOCs. #threatintel

— Bad Packets (@bad_packets)

There are now reports that this vulnerability is being used to implant cryptocurrency miners.

this log4shell payload is… a coin miner

the vulnerability has arrived pic.twitter.com/XUR7I5ydpP

— Kevin Beaumont (@GossiTheDog)

Proof of concept

The first PoC for CVE-2021-44228 was released on December 9 prior to its CVE identifier being assigned. At the time this blog post was published, there were an additional several PoCs available on GitHub.

Log4j 2.15.0 requires Java 8. Therefore, organizations that use Java 7 will need to upgrade before being able to update to the patched version of Log4j.

Apache advises that if patching is not immediately possible, there are three mitigation routes that can be taken to thwart attempts to exploit this vulnerability:

Mitigation Applicable Versions
Set log4j.formatMsgNoLookups or Dlog4j.formatMsgNoLookups to true Log4j 2.10 or greater
Use %m{nolookups} in the PatternLayout configuration Log4j 2.7 or greater
Remove JdniLookup and JdniManager classes from log4j-core.jar All Log4j 2 versions

Because Log4j is included in a number of web applications and used by a variety of cloud services, the full scope of this vulnerability won’t be known for some time. However, at the time this blog post was published, some products and services that were confirmed to be vulnerable include:

Product/Service Confirmed Affected
Minecraft Yes
Steam Yes
Apple iCloud Yes
Tencent Yes
Twitter Yes
Baidu Yes
Didi Yes
Cloudflare Yes
Amazon Yes
Tesla Yes
ElasticSearch Yes
Ghidra Yes

A GitHub repository is being maintained that highlights the attack surface of this vulnerability.

Identifying affected systems

A list of Tenable plugins to identify this vulnerability will appear here as they’re released. Currently (as of December 11) the following 5 plugins have been released (available in plugin feed 202112110647 and later)

Tenable has released scan templates for Tenable.io, Tenable.sc and Nessus Professional which are pre-configured to allow quick scanning for this vulnerability. In addition, Tenable.io customers have a new dashboard and widgets in the widgets library. Tenable.sc users also have a new Log4Shell dashboard. To ensure your scanner has the latest available plugins, Tenable recommends manually updating your plugin set. Nessus users, including Tenable.io Nessus scanners, can use the following Nessus CLI command:

nessuscli fix –secure –delete feed_auto_last

For more information on using nessuscli, please refer to this article.

Tenable.sc users can manually update plugins using the [Update] links in the Plugins/Feed Configuration UI as shown in the following screenshot

Organizations that don’t currently have a Tenable product can sign up for a free trial of Nessus Professional to scan for this vulnerability.

Learn more about Tenable, the first Cyber Exposure platform for holistic management of your modern attack surface.

Get a free 30-day trial of Tenable.io Vulnerability Management.

This content was originally published here.

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