Log4j vulnerabilities and the long slog through remediation and risk management.
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Log4j vulnerabilities are going to be with us for some time. They're undergoing active exploitation, and fixing them will require vigilance and attention to detail over the long haul.

Log4j vulnerabilities and the long slog through remediation and risk management.

Direct, flat, and sobering advice from Redmond.

Microsoft Security yesterday updated its Guidance for preventing, detecting, and hunting for exploitation of the Log4j 2 vulnerability. It's clear, sobering, and worth quoting in full:

"The Log4j vulnerabilities represent a complex and high-risk situation for companies across the globe. This open-source component is widely used across many suppliers’ software and services. By nature of Log4j being a component, the vulnerabilities affect not only applications that use vulnerable libraries, but also any services that use these applications, so customers may not readily know how widespread the issue is in their environment. Customers are encouraged to utilize scripts and scanning tools to assess their risk and impact. Microsoft has observed attackers using many of the same inventory techniques to locate targets. Sophisticated adversaries (like nation-state actors) and commodity attackers alike have been observed taking advantage of these vulnerabilities. There is high potential for the expanded use of the vulnerabilities.

"Exploitation attempts and testing have remained high during the last weeks of December. We have observed many existing attackers adding exploits of these vulnerabilities in their existing malware kits and tactics, from coin miners to hands-on-keyboard attacks. Organizations may not realize their environments may already be compromised. Microsoft recommends customers to do additional review of devices where vulnerable installations are discovered. At this juncture, customers should assume broad availability of exploit code and scanning capabilities to be a real and present danger to their environments. Due to the many software and services that are impacted and given the pace of updates, this is expected to have a long tail for remediation, requiring ongoing, sustainable vigilance."

The vulnerabilities are not only widespread and pervasive, but they're undergoing active exploitation by everyone from national intelligence services to low-grade skids running commodity hacks. A contribution to the "ongoing sustainable vigilance" Microsoft recommends may be found in the scanners and other advice the US Cybersecurity and Infrastructure Security Agency (CISA) has made available.

But both industry and government seem to be taking risk management seriously.

There's some good news about Log4j, however, and it lies in the way both the private and public sectors have responded to the vulnerability. The Washington Post reports a consensus that companies and government agencies have been noticeably more alert and responsive to the risks Log4j poses than they were in earlier instances of widespread vulnerabilities. In particular people see a much better sense of urgency and seriousness of approach than they witnessed in 2014, when Shellshock and Heartbleed were discovered and disclosed.

Since the effects of vulnerabilities in software libraries can cascade so rapidly, Dark Reading sees an object lesson in the Log4j incident: the experience should, the essay argues, lend more impetus to making software bills of materials the norm.

A brief Log4j vulnerability scorecard.

CVE Details now places the number of Log4j vulnerabilities at eight:

  1. CVE-2021-4510520: "Apache Log4j2 versions 2.0-alpha1 through 2.16.0 (excluding 2.12.3 and 2.3.1) did not protect from uncontrolled recursion from self-referential lookups. This allows an attacker with control over Thread Context Map data to cause a denial of service when a crafted string is interpreted. This issue was fixed in Log4j 2.17.0, 2.12.3, and 2.3.1."
  2. CVE-2021-45046502: "It was found that the fix to address CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete in certain non-default configurations. This could allows attackers with control over Thread Context Map (MDC) input data when the logging configuration uses a non-default Pattern Layout with either a Context Lookup (for example, $${ctx:loginId}) or a Thread Context Map pattern (%X, %mdc, or %MDC) to craft malicious input data using a JNDI Lookup pattern resulting in an information leak and remote code execution in some environments and local code execution in all environments. Log4j 2.16.0 (Java 8) and 2.12.2 (Java 7) fix this issue by removing support for message lookup patterns and disabling JNDI functionality by default."
  3. CVE-2021-4483220: "Apache Log4j2 versions 2.0-beta7 through 2.17.0 (excluding security fix releases 2.3.2 and 2.12.4) are vulnerable to a remote code execution (RCE) attack when a configuration uses a JDBC Appender with a JNDI LDAP data source URI when an attacker has control of the target LDAP server. This issue is fixed by limiting JNDI data source names to the java protocol in Log4j2 versions 2.17.1, 2.12.4, and 2.3.2."
  4. CVE-2021-44228502: "Apache Log4j2 2.0-beta9 through 2.12.1 and 2.13.0 through 2.15.0 JNDI features used in configuration, log messages, and parameters do not protect against attacker controlled LDAP and other JNDI related endpoints. An attacker who can control log messages or log message parameters can execute arbitrary code loaded from LDAP servers when message lookup substitution is enabled. From log4j 2.15.0, this behavior has been disabled by default. From version 2.16.0, this functionality has been completely removed. Note that this vulnerability is specific to log4j-core and does not affect log4net, log4cxx, or other Apache Logging Services projects."
  5. CVE-2021-4104502: "JMSAppender in Log4j 1.2 is vulnerable to deserialization of untrusted data when the attacker has write access to the Log4j configuration. The attacker can provide TopicBindingName and TopicConnectionFactoryBindingName configurations causing JMSAppender to perform JNDI requests that result in remote code execution in a similar fashion to CVE-2021-44228. Note this issue only affects Log4j 1.2 when specifically configured to use JMSAppender, which is not the default. Apache Log4j 1.2 reached end of life in August 2015. Users should upgrade to Log4j 2 as it addresses numerous other issues from the previous versions."
  6. CVE-2020-9488295: "Improper validation of certificate with host mismatch in Apache Log4j SMTP appender. This could allow an SMTPS connection to be intercepted by a man-in-the-middle attack which could leak any log messages sent through that appender."
  7. CVE-2019-17571502: "Included in Log4j 1.2 is a SocketServer class that is vulnerable to deserialization of untrusted data which can be exploited to remotely execute arbitrary code when combined with a deserialization gadget when listening to untrusted network traffic for log data. This affects Log4j versions up to 1.2 up to 1.2.17."
  8. CVE-2017-5645502: "In Apache Log4j 2.x before 2.8.2, when using the TCP socket server or UDP socket server to receive serialized log events from another application, a specially crafted binary payload can be sent that, when deserialized, can execute arbitrary code."