Exploited Ransomware

CVE-2021-44228

Apache Log4j2 Remote Code Execution Vulnerability

At a glance

Exploited. Added to CISA’s catalog of exploited vulnerabilities on December 10, 2021.

Used in ransomware attacks, according to CISA.

Affected product: Apache Log4j (category Frameworks and libraries, indicative classification). Name in CISA’s catalog: Apache Log4j2.

What should I do?

Apply the update from Apache; if none are available, stop using the product.

Deadline set by CISA for US federal agencies: 14 days (due December 24, 2021). It only binds those agencies, but it is a useful measure of urgency.

Apache security advisories page (general page, not the advisory for this vulnerability)
The vendor’s specific advisory is listed in the NVD references: CVE-2021-44228 on the NVD website.

Original text of the required action (CISA)

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 [lien retiré] are only acceptable until updates are available.

Timeline

December 10, 2021 Vulnerability published Publication date (NVD)
December 10, 2021 Exploitation confirmed Added to CISA’s KEV catalog
December 24, 2021 CISA deadline Remediation deadline set for US federal agencies

The facts, with their sources

Exploitation confirmed: Yes, on December 10, 2021 Date added to the catalog of exploited vulnerabilities. Exploitation itself may have started earlier. Source: KEV catalog, collected September 29, 2026 at 11:25 UTC
Ransomware: Known use Source: KEV catalog, collected September 29, 2026 at 11:25 UTC
Hunt for compromise: Not requested by CISA Source: KEV catalog, collected September 29, 2026 at 11:25 UTC
CISA required action: Apply the update from Apache; if none are available, stop using the product. Rewritten by this site from CISA’s original text. Source: KEV catalog, collected September 29, 2026 at 11:25 UTC
CISA deadline: December 24, 2021, 14 days Set for US federal agencies: a measure of urgency, not an obligation elsewhere. Source: KEV catalog, collected September 29, 2026 at 11:25 UTC
Vulnerability published: December 10, 2021 Source: National Vulnerability Database (NVD), collected September 29, 2026 at 11:29 UTC
Product according to CISA: Apache Log4j2 Filed by this site under “Frameworks and libraries” (indicative classification). Source: KEV catalog, collected September 29, 2026 at 11:25 UTC
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H Technical detail of the score: attack vector, complexity, impact. Source: National Vulnerability Database (NVD), collected September 29, 2026 at 11:29 UTC

Severity and activity

10.0 / 10 CVSS severity: critical

Score from the NVD. Collected Sep 29, 2026.

— Probability of exploitation in the next 30 days (EPSS)

FIRST’s EPSS model. Since exploitation is already confirmed, this figure is mostly useful to compare activity. Collected Sep 29, 2026.

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.

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

Summary from CISA (KEV catalog).

CERT-FR advisories

No advisory among the latest CERT-FR publications this site follows. That does not mean there are none.

Information reused under the Open Licence 2.0 (Etalab); the date of last update is shown for each advisory. This site is neither affiliated with nor endorsed by ANSSI.

Sources for this page

CISA KEV catalog: exploitation, date added, required action, deadline, ransomware.
NVD (NIST): CVSS severity, publication date, description, vendor references.
EPSS (FIRST): probability of exploitation.
CERT-FR: advisories and alerts (in French).
Brand and category: indicative classification by this site (method).