CVE-2021-44228
CRITICALCVE-2021-44228 is a critical-severity (CVSS 10) Improper Input Validation vulnerability in org.apache.logging.log4j:log4j-core. 384 public exploit references exist, so weaponization risk is real. O3 Security confirms whether CVE-2021-44228 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Remote code injection in Log4j
Exploitation Status
Actively exploited in the wild
- CISA’s SSVC triage classifies this CVE as under active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2021-44228.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2021-44228 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE sits: patch-first territory.
Where this sits among everything scored
Of 368,770 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
org.apache.logging.log4j:log4j-core☕org.apache.logging.log4j:log4j-core☕org.apache.logging.log4j:log4j-core☕com.guicedee.services:log4j-core☕org.xbib.elasticsearch:log4j☕uk.co.nichesolutions.logging.log4j:log4j-core☕org.ops4j.pax.logging:pax-logging-log4j2☕org.ops4j.pax.logging:pax-logging-log4j2+2 moreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.logging.log4j:log4j-core | ≥ 2.13.0&&< 2.15.0 | 2.15.0 |
| ☕Maven | org.apache.logging.log4j:log4j-core | ≥ 2.0-beta9&&< 2.3.1 | 2.3.1 |
| ☕Maven | org.apache.logging.log4j:log4j-core | ≥ 2.4&&< 2.12.2 | 2.12.2 |
| ☕Maven | com.guicedee.services:log4j-core | all versions | No fix |
| ☕Maven | org.xbib.elasticsearch:log4j | all versions | No fix |
| ☕Maven | uk.co.nichesolutions.logging.log4j:log4j-core | all versions | No fix |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
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Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.logging.log4j:log4j-core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.apache.logging.log4j:log4j-core to 2.15.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-44228 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2021-44228 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2021-44228. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This issue only affects log4j versions between 2.0 and 2.14.1. In order to exploit this flaw you need: - A remotely accessible endpoint with any protocol (HTTP, TCP, etc) that allows an attacker to send arbitrary data, - A log statement in the endpoint that logs the attacker controlled data. In Red Hat OpenShift…
Frequently Asked Questions
Is CVE-2021-44228 in your dependencies?
O3 detects CVE-2021-44228 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.