CriticalCVE-2021-44228

    Apache Log4j2 Remote Code Execution Vulnerability (CVE-2021-44228)

    Published Last modified In CISA KEV since Sources: SingCERT, Debian, OSV, Siemens ProductCERT, CVE.org, Red Hat

    What is affected, what to do

    The CVE-2021-44228 vulnerability allows for remote code execution (RCE) through the use of JNDI features in Apache Log4j2 that do not protect against attacker-controlled JNDI-related endpoints. An attacker can execute arbitrary code from LDAP servers by controlling log messages or parameters. This vulnerability is actively exploited in ransomware campaigns. Affected versions of log4j-core range from 2.0-beta9 to 2.15.0, excluding security releases 2.12.2, 2.12.3, and 2.3.1. An immediate update to version 2.16.0 or higher is urgently required to mitigate the vulnerability.

    The vulnerability is being actively exploited; treat it as a priority. CISA lists it as used in ransomware campaigns. Update log4j to version 2.3.1, xcode to version 13.3, synchro to version 6.2.4.2. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Apache Log4j2 gte 2.0-beta9..*

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    10.0

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    10.0

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: SingCERT, Debian, OSV, Siemens ProductCERT, CVE.org, Red Hat

    —

    EPSS score

    No value is available for this vulnerability.

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    255.17 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploitedSource: ANSSI / CERT-FR, CIRCL KEV How we classify
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    10.0 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    10.0
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-502, CWE-400, CWE-20

    Response and mitigation

    Why act now?

    Prioritisation rationale

    Log4Shell sits on KEV because it allows unauthenticated, network-reachable RCE with a trivially crafted payload against virtually any Java application using log4j-core 2.x — from perimeter proxies down to internal ERPs. Exploitation likelihood is among the highest ever recorded, scanning has been continuous since December 2021, and the CISA ransomware flag confirms adoption by extortion crews as an initial-access vector. Priority order: internet-facing Java services within 24 h, internal services within 72 h, embedded appliances per vendor advisory. Any system with unrestricted outbound internet access that also logs user-supplied input should be treated as compromised until forensics prove otherwise.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Upgrade every log4j-core instance to 2.17.1 (Java 8), 2.12.4 (Java 7) or 2.3.2 (Java 6). The interim 2.15.0 is insufficient (see CVE-2021-45046); 2.16.0 fixes JNDI but not CVE-2021-45105.
      • Build an inventory immediately: find / -name "log4j-core-*.jar" 2>/dev/null on Linux, PowerShell Get-ChildItem -Recurse -Filter log4j-core-*.jar on Windows. Prioritise internet-facing and DMZ systems; tools like Syft/Grype or the CISA Log4Shell scanner help at scale.
      • Where immediate patching is impossible, set the JVM flag -Dlog4j2.formatMsgNoLookups=true and restart the service. Alternatively strip the vulnerable class: zip -q -d log4j-core-*.jar org/apache/logging/log4j/core/lookup/JndiLookup.class.
      • Egress firewall: block outbound LDAP (389, 636), LDAPS, RMI (1099), DNS to unauthorised resolvers and HTTP/S from application servers to the internet. Callback to attacker infrastructure is the critical exploitation step — breaking it blunts the chain.
      • Check vendor advisories for commercial products (VMware vCenter, Cisco, Fortinet, IBM, Oracle, Elastic, Splunk) — many bundle log4j and require vendor hotfixes rather than manual JAR replacement.
      • Open a retrospective threat-hunt window back to 01 Dec 2021; mass exploitation preceded the vendor patch.

    2. Runbook step 2

      Mitigation layers

      • WAF/reverse-proxy: ruleset covering ${jndi:, ${lower:j}, ${upper:j}, ${::-j}, ${env:, ${sys:, Base64 variants and nested lookups. Use OWASP CRS 3.3.2+ or vendor signatures (Cloudflare, AWS WAF, F5 ASM, Imperva).
      • Network segmentation: place internet-facing Java services in dedicated VLANs with explicit egress allowlists. No default-route internet access for application servers, log pipelines or build agents.
      • JVM hardening: push log4j2.formatMsgNoLookups=true fleet-wide via JAVA_TOOL_OPTIONS. Additionally set com.sun.jndi.ldap.object.trustURLCodebase=false and com.sun.jndi.rmi.object.trustURLCodebase=false (default since JDK 11.0.1 / 8u191, must be explicit on older JVMs).
      • EDR/application control: block java spawning sh, bash, cmd.exe, powershell.exe, curl, wget, nc. This ancestry is almost always anomalous for Java app servers.
      • IAM: reduce Java service-account privileges, no domain-admin or cloud-root credentials. Rotate secrets held in environment variables — ${env:AWS_SECRET_ACCESS_KEY} has been actively abused as an exfiltration primitive.
      • SBOM discipline: extend CI/CD with dependency scanning (Dependency-Track, Trivy, Grype) to catch transitive log4j in fat JARs and container images.

    3. Runbook step 3

      Detection rules

      • Web access logs: regex for \$\{jndi:(ldap|ldaps|rmi|dns|iiop|nis|corba) across URI, headers (especially User-Agent, X-Forwarded-For, Referer, X-Api-Version) and POST bodies. Include obfuscations such as ${${lower:j}ndi:} and ${${::-j}${::-n}${::-d}${::-i}:}.
      • Sysmon EID 3 (Network Connect) or Zeek conn.log: outbound connections from java.exe/java to ports 1389, 389, 636, 1099, 53 towards public IPs. KQL example: DeviceNetworkEvents | where InitiatingProcessFileName == "java.exe" and RemotePort in (1389,389,636,1099) and RemoteIPType == "Public".
      • Sysmon EID 1 / EDR process creation: java as parent of sh, bash, powershell, cmd, curl, wget, whoami, id, base64. Sigma shape: parent_image|endswith: '\java.exe' and image|endswith: ('\cmd.exe','\powershell.exe').
      • DNS telemetry: lookups to known Interactsh, DNSlog, Burp Collaborator and canary domains plus high-entropy subdomains under .oast.site, .interact.sh, .dnslog.cn. Hunt randomised subdomains originating from app-server hosts.
      • Suricata/Snort: enable ET Open SIDs 2034647-2034668 and the subsequent log4j series. Alert on LDAP responses carrying javaClassName, javaSerializedData or javaFactory attributes.
      • Linux auditd/Falco: rule for writes into /tmp, /var/tmp, /dev/shm by the Java process UID followed by execve on those files.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    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: CSA/SingCERT, Debian Security Advisories, OSV (Open Source Vulnerabilities), siemens_advisory, cvelistv5, CISA KEV Catalog, redhat_csaf, NVD (NIST), CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    Apache Software FoundationApache Log4j2
    • ≥ 2.0-beta9
    • —
    apachelog4j
    • 2.0
    • 2.0.1 – < 2.3.1
    • 2.4.0 – < 2.12.2
    • 2.13.0 – < 2.15.0
    • —
    • 2.3.1
    • 2.12.2
    • 2.15.0
    applexcode
    • < 13.3
    • 13.3
    bentleysynchro
    • 6.1 – < 6.2.4.2
    • 6.2.4.2
    bentleysynchro_4d
    • < 6.4.3.2
    • 6.4.3.2
    ciscoadvanced_malware_protection_virtual_private_cloud_appliance
    • < 3.5.4
    • 3.5.4
    ciscoautomated_subsea_tuning
    • < 2.1.0
    • 02.01.00
    • 2.1.0
    • —
    ciscobroadworks
    • —
    • < 2021.11_1.162
    • —
    • 2021.11_1.162
    ciscobusiness_process_automation
    • 3.2.000.000 – < 3.2.000.009
    • 3.1.000.000 – < 3.1.000.044
    • < 3.0.000.115
    • 3.2.000.009
    • 3.1.000.044
    • 3.0.000.115
    ciscocloud_connect
    • < 12.6\(1\)
    • 12.6\(1\)
    ciscocloudcenter
    • < 4.10.0.16
    • 4.10.0.16
    ciscocloudcenter_cost_optimizer
    • < 5.5.2
    • 5.5.2
    ciscocloudcenter_suite
    • 5.4.1
    • 5.5.0
    • 5.5.1
    • 4.10.0.15
    • 5.3.0
    • —
    • —
    • —
    • —
    • —
    ciscocloudcenter_suite_admin
    • < 5.3.1
    • 5.3.1
    ciscocloudcenter_workload_manager
    • < 5.5.2
    • 5.5.2
    ciscocommon_services_platform_collector
    • 002.009\(001.001\)
    • 2.10.0 – < 2.10.0.1
    • 002.009\(000.001\)
    • 002.009\(001.000\)
    • < 2.9.1.3
    • 002.009\(000.002\)
    • 002.009\(001.002\)
    • 002.009\(000.000\)
    • 002.010\(000.000\)
    • —
    • 2.10.0.1
    • —
    • —
    • 2.9.1.3
    • —
    • —
    • —
    • —
    ciscoconnected_mobile_experiences
    • —
    • —
    ciscocontact_center_domain_manager
    • < 12.5\(1\)
    • 12.5\(1\)
    ciscocontact_center_management_portal
    • < 12.5\(1\)
    • 12.5\(1\)
    ciscocrosswork_data_gateway
    • < 2.0.2
    • 3.0.0
    • 2.0.2
    • —
    ciscocrosswork_network_automation
    • 2.0.0
    • 4.1.0
    • 4.1.1
    • 3.0.0
    • —
    • —
    • —
    • —
    • —
    • —
    ciscocrosswork_network_controller
    • < 2.0.1
    • 3.0.0
    • 2.0.1
    • —
    ciscocrosswork_optimization_engine
    • 3.0.0
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianapache-log4j2bullseye
    Linuxdebianapache-log4j2buster
    Linuxdebiandebian_linux10.0
    Linuxdebiandebian_linux11.0
    Linuxdebiandebian_linux9.0
    Othersiemens6bk1602-0aa12-0tp0_firmware—
    Othersiemens6bk1602-0aa22-0tp0_firmware—
    Othersiemens6bk1602-0aa32-0tp0_firmware—
    Othersiemens6bk1602-0aa42-0tp0_firmware—
    Othersiemens6bk1602-0aa52-0tp0_firmware—
    Otherfedoraprojectfedora34
    Otherfedoraprojectfedora35
    Otherciscofxos6.2.3
    Otherciscofxos6.3.0
    Otherciscofxos6.4.0
    Otherciscofxos6.5.0
    Otherciscofxos6.6.0
    Otherciscofxos6.7.0
    Otherciscofxos7.0.0
    Otherciscofxos7.1.0
    Othersiemenssppa-t3000_ses3000_firmware—
    Otherciscounified_sip_proxy—
    Otherciscounified_workforce_optimization—

    Weakness classes (CWE)

    • CWE-502Deserialization of Untrusted Data

      Base

      The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.

      Entry at MITRE CWE-502

    • CWE-400Uncontrolled Resource Consumption

      Class

      The product does not properly control the allocation and maintenance of a limited resource.

      Entry at MITRE CWE-400

    • CWE-20Improper Input Validation

      Class

      The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

      Entry at MITRE CWE-20

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    CIRCL KEVvulnerability.circl.lu (opens in a new tab)actively exploited
    ANSSI / CERT-FRLicence Ouverte 2.0, as of CERTFR-2021-ALE-022 – [MaJ] Vulnérabilité dans Apache Log4j (clôturée 2022-05-04) (opens in a new tab)cert.cyber.gouv.fractively exploited
    Packet StormApache Log4j2 2.14.1 Remote Code Execution (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormVMware Security Advisory 2021 0028 (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormApache Log4j2 2.14.1 Information Disclosure (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormApache Log4j2 2.14.1 Remote Code Execution (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormLog4j2 Log4Shell Regexes (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormLog4j Payload Generator (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormL4sh Log4j Remote Code Execution (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormLog4j Remote Code Execution Word Bypassing (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet Stormlog4j scan Extensive Scanner (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormVMware Security Advisory 2021 0028.4 (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormLog4Shell HTTP Header Injection (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormVMware vCenter Server Unauthenticated Log4Shell JNDI Injection Remote Code Execution (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormUniFi Network Application Unauthenticated Log4Shell Remote Code Execution (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormOpen Xchange App Suite 7.10.x Cross Site Scripting Command Injection (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormMobileIron Log4Shell Remote Command Execution (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormAD Manager Plus 7122 Remote Code Execution (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    PoC-in-GitHub (nomi-sec)cs50-cybersecurity-final-project (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)vulhub-log4j-cve-2021-44228 (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)log4-Java-logging-poc (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)exp-logpresso-CVE-2021-44228-Scanner (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)cve-2021-44228-lab (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)log4shell-audit (opens in a new tab)github.comPoC (publicly reported)reported, not verified

    References & sources

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Product identifiers remappedNVD

      Product mapping changed:
      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationchanged
      OR *cpe:2.3:a:cisco:firepower_threat_defense:6.6.0:*:*:*:*:*:*:*
      OR *cpe:2.3:a:cisco:secure_firewall_threat_defense:6.6.0:*:*:*:*:*:*:*

      Source identifier: nvd@nist.gov

    2. Product identifiers remappedNVD

      Product mapping changed:
      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationchanged
      OR *cpe:2.3:a:cisco:firepower_threat_defense:7.0.0:*:*:*:*:*:*:*
      OR *cpe:2.3:a:cisco:secure_firewall_threat_defense:7.0.0:*:*:*:*:*:*:*

      Source identifier: nvd@nist.gov

    3. Product identifiers remappedNVD

      Product mapping changed:
      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationchanged
      OR *cpe:2.3:a:cisco:firepower_threat_defense:6.7.0:*:*:*:*:*:*:*
      OR *cpe:2.3:a:cisco:secure_firewall_threat_defense:6.7.0:*:*:*:*:*:*:*

      Source identifier: nvd@nist.gov

    4. Product identifiers remappedNVD

      Product mapping changed:
      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationchanged
      OR *cpe:2.3:a:cisco:firepower_threat_defense:6.2.3:*:*:*:*:*:*:*
      OR *cpe:2.3:a:cisco:secure_firewall_threat_defense:6.2.3:*:*:*:*:*:*:*

      Source identifier: nvd@nist.gov

    5. Product identifiers remappedNVD

      Product mapping changed:
      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationchanged
      OR *cpe:2.3:a:cisco:firepower_threat_defense:6.4.0:*:*:*:*:*:*:*
      OR *cpe:2.3:a:cisco:secure_firewall_threat_defense:6.4.0:*:*:*:*:*:*:*

      Source identifier: nvd@nist.gov

    Show 3 older changes

    1. Product identifiers remappedNVD

      Product mapping changed:
      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationchanged
      OR *cpe:2.3:a:cisco:firepower_threat_defense:6.3.0:*:*:*:*:*:*:*
      OR *cpe:2.3:a:cisco:secure_firewall_threat_defense:6.3.0:*:*:*:*:*:*:*

      Source identifier: nvd@nist.gov

    2. Product identifiers remappedNVD

      Product mapping changed:
      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationchanged
      OR *cpe:2.3:a:cisco:firepower_threat_defense:6.5.0:*:*:*:*:*:*:*
      OR *cpe:2.3:a:cisco:secure_firewall_threat_defense:6.5.0:*:*:*:*:*:*:*

      Source identifier: nvd@nist.gov

    3. Product identifiers remappedNVD

      Product mapping changed:
      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationchanged
      OR *cpe:2.3:a:cisco:firepower_threat_defense:7.1.0:*:*:*:*:*:*:*
      OR *cpe:2.3:a:cisco:secure_firewall_threat_defense:7.1.0:*:*:*:*:*:*:*

      Source identifier: nvd@nist.gov

    Linked advisories

    Embed badge

    Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.

    Badge preview for CVE-2021-44228
    <a href="https://intel.neosec.eu/en/cve/CVE-2021-44228"><img src="https://intel.neosec.eu/badge/cve/CVE-2021-44228.svg?lang=en" alt="CVE-2021-44228 – NEOSEC Intel" height="20"></a>