CyberSecBulletin
CVE-2021-44228Exploited in the wildNVD status: Analyzed

Apache Log4j2 Remote Code Execution

Published Updated By the CyberSecBulletin desk

CVE-2021-44228 is a critical-severity improper neutralization of special elements used in an expression language statement vulnerability in Apache Log4j2 from Apache, with a CVSS 3.1 base score of 10.0 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version log4j-core* as the first without the flaw, so updating Apache Log4j2 to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on December 10, 2021, which means attacks have been observed in the wild, including in ransomware campaigns.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update Apache Log4j2 to log4j-core* or a later version.
  2. Update 6bk1602-0aa12-0tp0 Firmware to 2.7.0 or a later version.
  3. Update 6bk1602-0aa22-0tp0 Firmware to 2.7.0 or a later version.
  4. CISA's required action: For all affected software assets for which updates exist, the only acceptable remediation actions are: 1) Apply updates; OR 2) remove affected assets from agency networks. Temporary mitigations using one of the measures provided at https://www.cisa.gov/uscert/ed-22-02-apache-log4j-recommended-mitigation-measures are only acceptable until updates are available.
  5. Read the advisory on packetstormsecurity.com for workarounds and exact fixed builds.
  6. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
ApacheApache Log4j22.0-beta9 up to, but not including, log4j-core*log4j-core*
Siemens6bk1602-0aa12-0tp0 Firmwarebefore 2.7.02.7.0
Siemens6bk1602-0aa22-0tp0 Firmwarebefore 2.7.02.7.0
Siemens6bk1602-0aa32-0tp0 Firmwarebefore 2.7.02.7.0
Siemens6bk1602-0aa42-0tp0 Firmwarebefore 2.7.02.7.0
Siemens6bk1602-0aa52-0tp0 Firmwarebefore 2.7.02.7.0
ApacheLog4j2.0.1 up to, but not including, 2.3.1; 2.4.0 up to, but not including, 2.12.2; 2.13.0 up to, but not including, 2.15.0; 2.02.3.1, 2.12.2, 2.15.0
SiemensSppa-t3000 Ses3000 FirmwareNot specified in the recordNot stated
SiemensCapitalbefore 2019.1; 2019.12019.1
SiemensComosbefore 10.4.210.4.2
SiemensDesigo Cc Advanced Reports3.0; 4.0; 4.1; 4.2; 5.0; 5.1Not stated
SiemensDesigo Cc Info Center5.0; 5.1Not stated
SiemensE-car Operation Centerbefore 2021-12-132021-12-13
SiemensEnergy Engage3.1Not stated
SiemensEnergyip8.5; 8.6; 8.7; 9.0Not stated
SiemensEnergyip Prepaybefore 3.8.0.123.8.0.12
SiemensGma-managerbefore 8.6.2j-3988.6.2j-398
SiemensHead-end System Universal Device Integration SystemNot specified in the recordNot stated
SiemensIndustrial Edge ManagementNot specified in the recordNot stated
SiemensIndustrial Edge Management Hubbefore 2021-12-132021-12-13
SiemensLogo! Soft ComfortNot specified in the recordNot stated
SiemensMendixNot specified in the recordNot stated
SiemensMindspherebefore 2021-12-162021-12-16
SiemensNavigatorbefore 2021-12-132021-12-13
SiemensNxNot specified in the recordNot stated

Version data comes from the organisation that assigned the CVE; 35 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
ChangedThe attack can reach beyond the vulnerable component into other systems.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.110.0CriticalNVD
CVSS 3.110.0CriticalCISA (ADP)
CVSS 2.09.3HighNVD

Official description

Apache Log4j2 2.0-beta9 through 2.15.0 (excluding security releases 2.12.2, 2.12.3, and 2.3.1) 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 (along with 2.12.2, 2.12.3, and 2.3.1), 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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Neutralization of Special Elements used in an Expression Language Statement

The product constructs all or part of an expression language (EL) statement in a framework such as a Java Server Page (JSP) using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended EL statement before it is executed.

How developers prevent this class of flaw

  • Avoid adding user-controlled data into an expression interpreter when possible.
  • If user-controlled data must be added to an expression interpreter, one or more of the following should be performed: Validate that the user input will not evaluate as an expression Encode the user input in a way that ensures it is not evaluated as an expression
  • The framework or tooling might allow the developer to disable or deactivate the processing of EL expressions, such as setting the isELIgnored attribute for a JSP page to true.

More Improper Neutralization of Special Elements used in an Expression Language Statement vulnerabilities (CWE-917)

Timeline

  1. CVE record published.
  2. Added to CISA's Known Exploited Vulnerabilities catalogue.
  3. Deadline for US federal agencies to remediate, set by CISA.
  4. CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
  5. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Technical write-ups (may include proof of concept)

Recent Improper Neutralization of Special Elements used in an Expression Language Statement vulnerabilities

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