Posted on Wednesday December 22, 2021
Original release date: December 22, 2021 | Last revised: December 23, 2021The Cybersecurity and Infrastructure Security Agency (CISA), the Federal Bureau of Investigation (FBI), National Security Agency (NSA), Australian Cyber Security Centre (ACSC), Canadian Centre for Cyber Security (CCCS), the Computer Emergency Response Team New Zealand (CERT NZ), the New Zealand National Cyber Security Centre (NZ NCSC), and the United Kingdom’s National Cyber Security Centre (NCSC-UK) are releasing this joint Cybersecurity Advisory (CSA) to provide mitigation guidance on addressing vulnerabilities in Apache’s Log4j software library: CVE-2021-44228 (known as “Log4Shell”), CVE-2021-45046, and CVE-2021-45105. Sophisticated cyber threat actors are actively scanning networks to potentially exploit Log4Shell, CVE-2021-45046, and CVE-2021-45105 in vulnerable systems. According to public reporting, Log4Shell and CVE-2021-45046 are being actively exploited.
CISA, in collaboration with industry members of CISA’s Joint Cyber Defense Collaborative (JCDC), previously published guidance on Log4Shell for vendors and affected organizations in which CISA recommended that affected organizations immediately apply appropriate patches (or apply workarounds if unable to upgrade), conduct a security review, and report compromises to CISA or the FBI. CISA also issued an Emergency Directive directing U.S. federal civilian executive branch (FCEB) agencies to immediately mitigate Log4j vulnerabilities in solution stacks that accept data from the internet. This joint CSA expands on the previously published guidance by detailing steps that vendors and organizations with IT and/or cloud assets should take to reduce the risk posed by these vulnerabilities.
These steps include:
This CSA also provides guidance for affected organizations with operational technology (OT)/industrial control systems (ICS) assets.
Log4j is a Java-based logging library used in a variety of consumer and enterprise services, websites, applications, and OT products. These vulnerabilities, especially Log4Shell, are severe—Apache has rated Log4Shell and CVE-2021-45046 as critical and CVE-2021-45105 as high on the Common Vulnerability Scoring System (CVSS). These vulnerabilities are likely to be exploited over an extended period. CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK strongly urge all organizations to apply the recommendations in the Mitigations section.
CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK encourage leaders of organizations to review NCSC-UK’s blog post, Log4j vulnerability: what should boards be asking?, for information on Log4Shell’s possible impact on their organization as well as response recommendations.
Note: this is an evolving situation, and new vulnerabilities are being discovered. CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK will update this CSA as we learn more about this exploitation and have further guidance to impart.
Click here for a PDF version of this report.
The information in this report is being provided “as is” for informational purposes only. CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK do not endorse any commercial product or service, including any subjects of analysis. Any reference to specific commercial products, processes, or services by service mark, trademark, manufacturer, or otherwise, does not constitute or imply endorsement, recommendation, or favoring by CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, or NCSC-UK.
Log4Shell, disclosed on December 10, 2021, is a remote code execution (RCE) vulnerability affecting Apache’s Log4j library, versions 2.0-beta9 to 2.14.1. The vulnerability exists in the action the Java Naming and Directory Interface (JNDI) takes to resolve variables. Affected versions of Log4j contain JNDI features—such as message lookup substitution—that do not protect against adversary-controlled Lightweight Directory Access Protocol (LDAP), Domain Name System (DNS), and other JNDI-related endpoints.
An adversary can exploit Log4Shell by submitting a specially crafted request to a vulnerable system that causes that system to execute arbitrary code. The request allows the adversary to take full control over the system. The adversary can then steal information, launch ransomware, or conduct other malicious activity.
CVE-2021-45046, disclosed on December 13, 2021, enables a remote attacker to cause RCE, a denial-of-service (DoS) condition, or other effects in certain non-default configurations. This vulnerability affects all versions of Log4j from 2.0-beta9 through 2.12.1 and 2.13.0 through 2.15.0. In response, Apache released Log4j version 2.16.0 (Java 8).
CVE-2021-45105, disclosed on December 16, 2021, enables a remote attacker to cause a DoS condition or other effects in certain non-default configurations. According to Apache, when the logging configuration uses a non-default Pattern Layout with a Context Lookup (for example, $${ctx:loginId}), attackers with control over Thread Context Map (MDC) input data can craft malicious input data that contains a recursive lookup, resulting in a StackOverflowError that will terminate the process. In response, Apache released Log4j version 2.17.0 (Java 8).
Log4Shell and CVE-2021-45046—rated as critical vulnerabilities by Apache—are severe because Java is used extensively across IT and OT platforms, they are easy to exploit, and applying mitigations is resource intensive. Log4Shell is especially critical because it allows malicious actors to remotely run code on vulnerable networks and take full control of systems.
According to public reporting, exploitation of Log4Shell began on or around December 1, 2021, and a proof-of-concept exploit is publicly available for this vulnerability. The FBI has observed attempted exploitation and widespread scanning of the Log4j vulnerability to gain access to networks to deploy cryptomining and botnet malware. The FBI assesses this vulnerability may be exploited by sophisticated cyber threat actors and incorporated into existing cyber criminal schemes that are looking to adopt increasingly sophisticated obfuscation techniques. According to public reporting, CVE-2021-45046 is being actively exploited as well.
CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK assess that exploitation of these vulnerabilities, especially Log4Shell, is likely to increase and continue over an extended period. Given the severity of the vulnerabilities and likely increased exploitation, CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK strongly urge all organizations to apply the recommendations in the Mitigations section to identify, mitigate, and update affected assets.
For more information on these vulnerabilities, see the Apache Log4j Security Vulnerabilities webpage.
CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK encourage vendors to:
CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK recommend that affected organizations take the following steps to patch these vulnerabilities in their IT and cloud assets and initiate threat hunting to detect possible compromise. Organizations with OT/ICS environments should review the Organizations with OT/ICS Assets section for additional guidance. Note: this guidance includes resources that may or may not be possible for all organizations. CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK recommend that organizations apply the mitigations listed in this advisory to the extent allowed by their environments.
1. Identify vulnerable assets in your environment.
Knowing where Log4j and other affected products exist in your environment is key for protecting your networks.
Additional resources for detecting vulnerable instances of Log4j are identified below. CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK will update the sources for detection rules as we obtain them. Note: due to the urgency to share this information, CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK have not yet validated this content.
2. Mitigate known and suspected vulnerable assets in your environment.
A. Treat known and suspected vulnerable assets as compromised. These assets should be isolated until they are mitigated and verified (step 2.D). The method of isolation that you should use depends on the criticality of the asset. Possible isolation methods include:
B. Patch Log4j and other affected products to the latest version.
Note: if your organization is unable to immediately identify and patch vulnerable instances of Log4j, apply appropriate workarounds. CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK recommend using vendor-provided mitigations when available. Due to the rapidly evolving situation, these workarounds should not be considered permanent fixes and organizations should apply the appropriate patch as soon as it is made available. Additional mitigations are identified below; however, organizations should use these mitigations at their own risk as they may be incomplete, temporary, or cause harmful effects, such as application instability, a DoS condition, or log evasion.
Jndilookup.class from the class path. [1]Jndilookup.class. Note: removal of the JndiManager will cause the JndiContextSelector and JMSAppender to no longer function). [2]C. Keep an inventory of known and suspected vulnerable assets and what is done with them throughout this process. It is important to track patching because malicious cyber actors may compromise an asset and then patch it to protect their operations. Organizations should keep a meticulous record of vulnerable assets they have patched to identify whether a threat actor may have patched an asset.
D. Verify the mitigation has worked, if possible.
3. Initiate hunt and incident response procedures. Given the widespread exploitation of this vulnerability, CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK encourage all organizations to assume their assets that use Log4j may have been compromised and initiate hunt procedures.
A. Hunt for signs of exploitation and compromise.
Additional resources to detect possible exploitation or compromise are identified below. Note: due to the urgency to share this information, CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK have not yet validated this content.
B. If compromise is detected, organizations should:
4. Evaluate and apply other mitigations.
A. Remain alert to changes from vendors for the software on the asset, and immediately apply updates to assets when notified by a vendor that their product has a patch for this vulnerability. Additionally, see CISA's GitHub repository for known affected products and patch information. CISA will continually update the repository as vendors release patches.
B. Continue to monitor Log4J assets closely. Continually use signatures and indicators of compromise that may indicate exploitation.
C. Continue to monitor the Apache Log4j Security Vulnerabilities webpage for new updates. Note: as this is an evolving situation and new vulnerabilities in Log4J are being discovered, organizations should ensure their Apache Log4j is up to date. Identify the software your enterprise uses and stay on top of updates as these may be superseded by other updates and fixes.
D. Block specific outbound Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) network traffic.
Note: blocking attacker internet IP addresses during this event is difficult due to the high volume of scanning from non-malicious researchers and vendors. The false positives on IP addresses are high. Organizations should focus on looking for signs of successful exploitation and not scans.
Affected Organizations with OT/ICS Assets
Due to the pervasiveness of the Apache Log4j software library—and the integration of the library in operational products—CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK strongly recommend that OT asset owners and operators review their operational architecture and enumerate the vulnerability status against current product alerts and advisories. If a product does not have a security advisory specifically addressing the status of the vulnerability, treat it with additional protections. CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK urge patching or deployment of mitigations to reduce the risk of the threat of these vulnerabilities.
Note: CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK recommend prioritizing patching IT devices, especially those with internet connectivity. Affected internet-facing devices as well as laptops, desktops, and tablets are especially susceptible to exploitation of these vulnerabilities. OT/ICS devices—if segmented appropriately from the IT environment—do not face the internet and, as such, have a smaller attack surface to this vulnerability. Exploitation of IT devices may affect OT/ICS devices if there is insufficient network segmentation that prevents lateral movement.
CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK recommend that OT/ICS asset owner/operators take the following guidance into consideration:
When remote access is required, use secure methods such as virtual private networks (VPNs), recognizing VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize that a VPN is only as secure as its connected devices.
CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK also remind organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.
CISA also provides a section for control systems security recommended practices on the ICS webpage on cisa.gov. Several recommended practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.
Additional mitigation guidance and recommended practices are publicly available on the ICS webpage on cisa.gov in the Technical Information Paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies.
Organizations observing any suspected malicious activity should follow their established internal procedures and consider reporting compromises immediately.
For more information, resources, and general guidance, including resources and mitigation guidance from industry members of JCDC, see CISA’s webpage Apache Log4j Vulnerability Guidance. Note: due to the prominent and ever evolving nature of this vulnerability, there are multiple unverified published guidance documents that are geared towards Log4j vulnerabilities. CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, and NCSC-UK encourage all organizations to verify information with trusted sources, such CISA, the FBI, NSA, ACSC, CCCS, CERT NZ, NZ NCSC, NCSC-UK vendors.
This product is provided subject to this Notification and this Privacy & Use policy.
Phone: +1-989-776-2080
Toll Free: +1-855-674-2968
Email: info (at) netservicesgroup dot com
DUNS 155892800
SPIN 143027933
100% Michigan
NSG is owned & operated, offering enterprise-level IT service & support, right in your own back yard.