CVE-2021-44228, a Log4j vulnerability, was announced on Dec. 10. “Log4Shell” exploits remote code execution via a log entry to access a machine.
Java logging library Log4j is open-source. Log4j isn’t the default Java logging library, although it’s frequently used in production applications. You may not have heard of Java unless you’re a developer, yet it’s used in many unexpected domains.
JNDI’s flaw (Java Naming and Directory Interface). JNDI lets log variables request network-accessible resources. This feature allows code to be performed locally with the same permissions as the calling program, enriching logs. URIs to java objects served by an LDAP server are injected into the logs. LDAP provides arbitrary code execution. Vulnerable versions include 2.0.x to 2.14.x.
Today, crypto-mining malware uses the vulnerability. Simple exploit likely used to launch more attacks. Ransomware, data exfiltration, and system pivots.
Two flaws were found on 22/12/2013. 2.15.0 and 2.16.0 are likewise susceptible.
- CVE-2021-45105: Risk of Denial of Service (DOS)
- CVE-2021-45046: Risk of information leak, remote code execution in some situations, local code execution in all
Versions 2.17.0 (Java 8), 2.12.3 (Java 7), and 2.3.1 are correct (Java 6). Three versions patch vulnerabilities.
Vulnerability assessment
Prioritize your investigation to find vulnerable systems.
Public systems checked
Start promptly researching public IP-addressed systems. Any internet-connected computer is vulnerable. Non-Java apps can use Log4j Java. Consider all application log-generating behaviors. First, log HTTP or login form inquiries. Examine post-authentication activities, especially on untrusted platforms.
Crawling apps
If you have the source code, look for log4j. This identifies log types and attacks entry sites. In your code repository, look for “import org.apache.log4j.” You’ll see all library apps. It narrows the search.
OS check
A legitimate application using a vulnerable version of log4j doesn’t make your server insecure. Most Linux distributions have Log4j. If your SysAdmins don’t use strict hardening, you may have it. Check Log4j on all plans. Manual installation or application bundling are both options. Search for jar files containing “log4j” to see how it’s used and find problem areas.
Free/commercial software
Next, check software security pages. Community and security researchers create Log4j websites. It’s neither perfect nor exhaustive, but you’ll find Log4j. Editors’ knowledge isn’t always enough to tell if you’re at risk, but it can encourage further investigation.
Others
Software or devices without an active community are hard to assess. Any black box could use Log4j. This portends security incidents.
Instructions
In the following months and years, Log4shell will be difficult. Experts will soon uncover new weaknesses and attack protocols. Safety hygiene and best practices can limit hazards.
- Patch and check
- Inventory software.
- Monitor attack vectors and editor announcements.
- Reduce attack impact by segmenting systems.
- Use unprivileged accounts as possible.
- Block untrusted server egress
- Avoid unnecessary secrets and credentials on production servers.
- Block Log4Shell IPs and domains.
- WAF and filtering stop attacks (beginning with “jndi” is a good start).
- Log irregular behavior and egress connections.
- Test backups often
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