CVE-2021-45046

Apache Log4j2: Deserialization of Untrusted Data

As of , CVE-2021-45046 in Apache Log4j2 is on CISA's list of exploited vulnerabilities: CISA listed it on . Our patch-first group: Patch this week.

Exploited
Yes: CISA listed it on 1 May 2023
US federal deadline
22 May 202321 days after CISA listed it. US federal civilian agencies must fix it by then.
Used in ransomware campaigns
Known
EPSS score
0.99Higher than 99% of the CVEs EPSS scores. EPSS estimates the chance of exploitation activity in the next 30 days.
EPSS when listed
0.97 on 1 May 2023EPSS on the day CISA listed it.
Public exploit
1 Metasploit module
Fix
Vendor advice: logging.apache.orgLinks below, from CISA's entry.

What CISA says to do

Apply updates per vendor instructions.

CISA's required action

What the flaw is

Apache Log4j2 contains a deserialization of untrusted data vulnerability due to the incomplete fix of CVE-2021-44228, where the Thread Context Lookup Pattern is vulnerable to remote code execution in certain non-default configurations.

CISA's description

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.

The CVE record's description, from apache

CVE published
14 December 2021
Assigned by
apache
CVSS
9.0 Critical (CVSS 3.1, from CISA-ADP)
CWE-917
Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection')
CISA SSVC, exploitation
active
CISA SSVC, automatable
no
CISA SSVC, technical impact
total

Timeline

  1. The CVE record was published.
  2. CISA added it to its list of exploited vulnerabilities.
  3. The US federal deadline to fix it.

Public exploits

Facts from Metasploit's module list and Exploit-DB's index; we never copy exploit code.

  • Metasploit: Log4Shell HTTP Scannerauxiliary module, rank normal

Log4j2: other exploited entries

VulnerabilityProductOur groupListedDeadlineEPSS
CVE-2021-44228Remote Code ExecutionApache Log4j2Patch this weekRansomware use; Metasploit module; EPSS 0.990.99

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