Security Affairspublished Dec 11, 10:05 UTC (Dec 11, 2021)ingested Sep 10, 06:12 UTC@securityaffairs

Logout4Shell, a vaccine for Log4Shell Apache Log4j RCE

criticalVulnerabilityimportance 60CVE-2021-44228

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Tagscve-2021-44228 vulnerability

Vulnerabilities mentionedAll →

CVE	Vulnerability	CVSS	EPSS	Flags	Affected	Exposure	Published
CVE-2021-44228	JNDI Injection Remote Code Execution in Apache Log4j2 (Log4Shell) Apache Log4j2, an extremely widely used Java logging library, fails to protect its JNDI lookup feature against attacker-controlled JNDI-related endpoints (CWE-20, CWE-502), so crafted text processed by the logger causes the Java runtime to fetch and load attacker-supplied objects, leading to remote code execution. The flaw is triggered whenever attacker-controlled input reaches the logging API and is parsed for JNDI lookups, a pattern common in web servers and enterprise Java applications that log user-supplied fields such as headers or form values. Successful exploitation yields arbitrary code execution under the privileges of the affected application, giving attackers a foothold for lateral movement, data theft, and ransomware deployment. Any Java application or product that ships or bundles an affected Apache Log4j2 release is exposed, making this one of the most broadly deployed vulnerabilities ever disclosed. Exploitation is confirmed in the wild: CISA added it to the Known Exploited Vulnerabilities catalog on 2021-12-10 with known ransomware use, and EPSS assigns a 100% probability of exploitation within 30 days. Do: Inventory all Java applications and dependencies for Apache Log4j2 and apply the vendor's patched updates, or remove affected assets from the network, as required by CISA's KEV catalog. Where updates are not yet available, use the temporary mitigations in CISA's ED-22-02 recommended-mitigation guidance, such as disabling message lookups, only until patches are applied. Prioritize internet-facing and business-critical systems and hunt for exploitation activity given known ransomware use.	10.0	100%	KEV ransomware PoC ×9	Apache Log4j2	masshundreds of millions of Java applications/devices, with hundreds of thousands of internet-exposed services	Dec 10, 2021

CVE

Vulnerability

CVSS

EPSS

Flags

Affected

Exposure

Published

CVE-2021-44228

JNDI Injection Remote Code Execution in Apache Log4j2 (Log4Shell)

Apache Log4j2, an extremely widely used Java logging library, fails to protect its JNDI lookup feature against attacker-controlled JNDI-related endpoints (CWE-20, CWE-502), so crafted text processed by the logger causes the Java runtime to fetch and load attacker-supplied objects, leading to remote code execution. The flaw is triggered whenever attacker-controlled input reaches the logging API and is parsed for JNDI lookups, a pattern common in web servers and enterprise Java applications that log user-supplied fields such as headers or form values. Successful exploitation yields arbitrary code execution under the privileges of the affected application, giving attackers a foothold for lateral movement, data theft, and ransomware deployment. Any Java application or product that ships or bundles an affected Apache Log4j2 release is exposed, making this one of the most broadly deployed vulnerabilities ever disclosed. Exploitation is confirmed in the wild: CISA added it to the Known Exploited Vulnerabilities catalog on 2021-12-10 with known ransomware use, and EPSS assigns a 100% probability of exploitation within 30 days.

Do: Inventory all Java applications and dependencies for Apache Log4j2 and apply the vendor's patched updates, or remove affected assets from the network, as required by CISA's KEV catalog. Where updates are not yet available, use the temporary mitigations in CISA's ED-22-02 recommended-mitigation guidance, such as disabling message lookups, only until patches are applied. Prioritize internet-facing and business-critical systems and hunt for exploitation activity given known ransomware use.

10.0

100%

KEV ransomware PoC ×9

Apache Log4j2

masshundreds of millions of Java applications/devices, with hundreds of thousands of internet-exposed services

Dec 10, 2021

Full article342 words · extracted from securityaffairs.com · click to collapse

Pierluigi Paganini December 11, 2021

Cybereason researchers released a “vaccine” that mitigates the critical ‘Log4Shell’ Apache Log4j code execution vulnerability.

Chinese security researcher p0rz9 publicly disclosed a Proof-of-concept exploit for a critical remote code execution zero-day vulnerability, tracked a CVE-2021-44228 (aka Log4Shell), in the Apache Log4j Java-based logging library.

https://twitter.com/P0rZ9/status/1468949890571337731

p0rz9 revealed that the CVE-2021-44228 can only be exploited if the log4j2.formatMsgNoLookups option is set to false.

The Log4j is widely used by both enterprise apps and cloud services, including Apple iCloud and Steam.

A remote, unauthenticated attacker can exploit the CVE-2021-44228 to execute arbitrary code on a vulnerable system leading to a complete system takeover.

The vulnerability was discovered by researchers from Alibaba Cloud’s security team that notified the Apache Foundation on November 24. According to the experts, the vulnerability is easy to exploit and does not require special configuration, for this reason, it received a CVSSv3 score of 10/10. Researchers pointed out that Apache Struts2, Apache Solr, Apache Druid, Apache Flink are all affected by this vulnerability.

Now researchers from cybersecurity firm Cybereason have released a script that works as a “vaccine”(dubbed Logout4Shell) that allows remotely mitigating the Log4Shell vulnerability by turning off the “trustURLCodebase” setting in vulnerable instances of the library.

“While the best mitigation against this vulnerability is to patch log4j to 2.15.0 and above, in Log4j version (>=2.10) this behavior can be mitigated by setting system property log4j2.formatMsgNoLookups to true or by removing the JndiLookup class from the classpath. Additionally, if the server has Java runtimes >= 8u121, then by default, the settings com.sun.jndi.rmi.object.trustURLCodebase and com.sun.jndi.cosnaming.object.trustURLCodebase are set to “false”, mitigating this risk. However, enabling these system property requires access to the vulnerable servers as well as a restart.” reads the GitHub Page set up for the Log4Shell project.

Cyberreson experts pointed out that enabling these system property requires access to the vulnerable servers, and the servers have to be restarted.

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Pierluigi Paganini

(SecurityAffairs – hacking, Logout4Shell)

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