CVE-2021-44228: in the CISA KEV catalogue

Apache Log4j2 Remote Code Execution Vulnerability. CISA added CVE-2021-44228 to the Known Exploited Vulnerabilities catalogue on 2021-12-10 with a default due date of 2021-12-24. Known ransomware campaign use: Known. Forensic triage flag: No.

Apache Log4j2 contains a vulnerability where JNDI features do not protect against attacker-controlled JNDI-related endpoints, allowing for remote code execution. (CISA description)

Vendor / product: Apache Log4j2
CWE: CWE-20, CWE-400, CWE-502
CISA 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.
EPSS: 100%, percentile 100 (scored 2026-11-03)

EPSS puts nearly every time in 100 odds (100%) on exploitation activity being observed in the next 30 days. Its score is higher than or equal to that of 100% of scored CVEs. This is a model estimate about exploitation anywhere, not about your environment.

Vendor and reference links (from CISA)

https://nvd.nist.gov/vuln/detail/CVE-2021-44228

Your own deadline under CISA BOD 26-04 depends on exposure, automatability and technical impact: work it out with the BOD 26-04 calculator.

Data dates. CISA KEV catalogue version 2026.11.03, released 2026-11-03, 1,767 entries (checked 2026-11-03). EPSS model v2026.06.15, scored 2026-11-03, 399,388 CVEs. Sources: CISA and FIRST (EPSS by FIRST; scores generated by Empirical Security). Copied to our own database and refreshed automatically; if a refresh fails, the previous copy keeps serving with its own date.

Frequently asked questions

Is CVE-2021-44228 in the CISA KEV catalogue?

Yes. CISA added CVE-2021-44228 (Apache Log4j2 Remote Code Execution Vulnerability) to the Known Exploited Vulnerabilities catalogue on 2021-12-10. CISA's default due date for it is 2021-12-24.

Is CVE-2021-44228 used in ransomware attacks?

CISA marks known ransomware campaign use as Known for CVE-2021-44228.

What should I do about CVE-2021-44228?

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.

Sources

CISA, Known Exploited Vulnerabilities Catalog (accessed 2026-11-03)
FIRST, Exploit Prediction Scoring System (EPSS) (EPSS by FIRST; scores generated by Empirical Security)
NVD record for CVE-2021-44228