Threat Signal Report

Log4j 2.17.1 Released for CVE-2021-44832

description-logo Description

NOTE: 12/30 IPS signature information added

FortiGuard Labs is aware of a newly disclosed remote code execution vulnerability affecting Log4j. Assigned CVE-2021-44832, this vulnerability allows for a remote code execution (RCE) attack where an attacker with permission to modify the logging configuration file can construct a malicious configuration using a JDBC Appender with a data source referencing a JNDI URI which can execute remote code.


There has been confusion on Twitter as to whether this is actually a remote code execution (RCE) or arbitrary code execution (ACE) vulnerability. Researcher Yaniv Naziry (@YNizry) initially stated today that a new RCE vulnerability related to Log4j is to be announced, and later retracted their initial statement confirming that it is indeed arbitrary code execution and not remote code execution.


Compounding matters, Apache classifies CVE-2021-44832 as a remote code execution vulnerability. In the writeup for CVE-2021-44832, Apache states that the attacker needs permission to "modify the logging configuration file" to successfully exploit this vulnerability which is not indicative of an RCE. CVE-2021-44832 is fixed in Log4j 2.17.1 (Java 8), 2.12.4 (Java 7) and 2.3.2 (Java 6).


What is Arbitary Code Execution and Remote Code Execution?

Arbitrary code execution (ACE) results from a flaw in software or hardware that allows for an attacker to target a specific machine or process to run code of their choice. Remote Code Execution (RCE) allows for an attacker to arbitrarily execute code remotely on a wide area network, such as the Internet.


What Versions of Log4J are Affected?

All versions from 2.0-alpha7 to 2.17.0, excluding 2.3.2 and 2.12.4.


What is the CVSS Score?

6.6 (MODERATE)


What is the Status of Coverage?

Customers running the latest IPS definitions (19.231) are protected against exploitation of CVE-2021-44832 by the following signature:

Apache.Log4j.Error.Log.Configuration.File.Remote.Code.Execution


What Mitigation is Suggested?

According to Apache, the following Mitigation is available:


Log4j 1.x mitigation

Log4j 1.x is not impacted by this vulnerability.


Log4j 2.x mitigation

Upgrade to Log4j 2.3.2 (for Java 6), 2.12.4 (for Java 7), or 2.17.1 (for Java 8 and later).

In prior releases confirm that if the JDBC Appender is being used it is not configured to use any protocol other than Java. Note that only the log4j-core JAR file is impacted by this vulnerability. Applications using only the log4j-api JAR file without the log4j-core JAR file are not impacted by this vulnerability. Also note that Apache Log4j is the only Logging Services subproject affected by this vulnerability. Other projects like Log4net and Log4cxx are not impacted by this.


Definitions

Traffic Light Protocol

Color When Should it Be used? How may it be shared?

TLP: RED

Not for disclosure, restricted to participants only.
Sources may use TLP:RED when information cannot be effectively acted upon by additional parties, and could lead to impacts on a party's privacy, reputation, or operations if misused. Recipients may not share TLP:RED information with any parties outside of the specific exchange, meeting, or conversation in which it was originally disclosed. In the context of a meeting, for example, TLP:RED information is limited to those present at the meeting. In most circumstances, TLP:RED should be exchanged verbally or in person.

TLP: AMBER

Limited disclosure, restricted to participants’ organizations.
Sources may use TLP:AMBER when information requires support to be effectively acted upon, yet carries risks to privacy, reputation, or operations if shared outside of the organizations involved. Recipients may only share TLP:AMBER information with members of their own organization, and with clients or customers who need to know the information to protect themselves or prevent further harm. Sources are at liberty to specify additional intended limits of the sharing: these must be adhered to.

TLP: GREEN

Limited disclosure, restricted to the community.
Sources may use TLP:GREEN when information is useful for the awareness of all participating organizations as well as with peers within the broader community or sector. Recipients may share TLP:GREEN information with peers and partner organizations within their sector or community, but not via publicly accessible channels. Information in this category can be circulated widely within a particular community. TLP:GREEN information may not be released outside of the community.

TLP: WHITE

Disclosure is not limited.
Sources may use TLP:WHITE when information carries minimal or no foreseeable risk of misuse, in accordance with applicable rules and procedures for public release. Subject to standard copyright rules, TLP:WHITE information may be distributed without restriction.