CVE-2021-44228: Log4Shell
CVE-2021-44228 (Log4Shell) is a remote code execution (jndi/ldap lookup injection) vulnerability in org.apache.logging.log4j:log4j-core (Maven). As of 2026-06-18 it carries a very high 100.0% probability of exploitation in the next 30 days (EPSS). It is fixed in 2.17.1 (2.15.0 first patched the RCE) — if you depend on an earlier version, upgrade.
| Severity | Critical |
|---|---|
| CVSS vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H |
| EPSS (exploit probability, 30d) | 100.0% · 100th percentile |
| Vulnerability type | Remote Code Execution (JNDI/LDAP lookup injection) |
| Affected package | org.apache.logging.log4j:log4j-core (Maven) |
| Fixed in | 2.17.1 (2.15.0 first patched the RCE) |
What is CVE-2021-44228?
A crafted string logged by a vulnerable Log4j 2 version triggers a JNDI lookup that loads and runs attacker-controlled code — unauthenticated remote code execution. One of the most exploited vulnerabilities ever disclosed.
Is CVE-2021-44228 exploitable?
CVE-2021-44228 has an EPSS score of 100.0% (100th percentile), meaning a very high 100.0% probability of exploitation in the next 30 days. Its CVSS vector is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H, which scores as Critical severity. It is a remote code execution (jndi/ldap lookup injection) issue.
What is the EPSS score for CVE-2021-44228?
As of 2026-06-18, the EPSS exploit-prediction score for CVE-2021-44228 is 100.0% (100th percentile). EPSS estimates the probability that a vulnerability will be exploited in the wild within the next 30 days and is recomputed daily by FIRST.org.
How do I fix CVE-2021-44228?
Upgrade org.apache.logging.log4j:log4j-core to 2.17.1 (2.15.0 first patched the RCE) or later. A crafted string logged by a vulnerable Log4j 2 version triggers a JNDI lookup that loads and runs attacker-controlled code — unauthenticated remote code execution. One of the most exploited vulnerabilities ever disclosed.
Am I affected by CVE-2021-44228?
You are affected if your project (directly or transitively) depends on a vulnerable version of org.apache.logging.log4j:log4j-core in the Maven ecosystem. Check your lockfile for the resolved version, or scan automatically with VulnFeed.
Check your own project automatically
Don't eyeball every dependency by hand. VulnFeed reads your lockfile, checks it against the same advisory data, and ranks findings by EPSS — free, no signup (10 scans/day):
curl -s https://vulnfeed-api.novadyne.ai/vulnscan/query \
-H 'content-type: application/json' \
-d '{"ecosystem":"npm","package":"PKG","version":"VERSION"}'
Or run it inside Claude Code with no API key — uvx vulnfeed-mcp — and just ask "scan this project for vulnerabilities."
Data sources: vulnerability metadata from OSV.dev and the National Vulnerability Database; exploit-probability (EPSS) from FIRST.org (recomputed daily; EPSS data shown here as of 2026-06-18). Page generated 2026-06-18.