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MEDIUM

CVE-2021-45105

CVSS v3

5.9

MEDIUM

EPSS Score

100.0 %

exploit probability, as of 2026-10-19

CISA KEV

No

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • org.apache.logging.log4j:log4j-coreMavenall versions · fixed in 2.3.1
  • org.ops4j.pax.logging:pax-logging-log4j2Mavenfrom 2.0.0 · fixed in 2.0.13

Vendor advisories

  • CVE-2021-45105 Red Hat Product Security33 products fixed · 4 known affected

    log4j-core: DoS in log4j 2.x with Thread Context Map (MDC) input data contains a recursive lookup and context lookup pattern

    log4j-api as a component of Red Hat Decision Manager 7 · log4j-core as a component of Red Hat Integration Camel Quarkus 1 · openshift3/ose-logging-elasticsearch5 as a component of Red Hat OpenShift Container Platform 3.11

  • RHSA-2022:1463 Red Hat Product Security3 products fixed

    Red Hat Security Advisory: Red Hat Single Sign-On 7.5.2 security update on RHEL 8

  • RHSA-2022:1462 Red Hat Product Security3 products fixed

    Red Hat Security Advisory: Red Hat Single Sign-On 7.5.2 security update on RHEL 7

  • RHSA-2022:1469 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: Red Hat Single Sign-On 7.5.2 security update

  • RHSA-2022:1299 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: Red Hat JBoss Enterprise Application Platform 7.4.4 security update

  • RHSA-2022:1297 Red Hat Product Security2 products fixed

    Red Hat Security Advisory: Red Hat JBoss Enterprise Application Platform 7.4.4 security update

15 more advisories

Full record on NVD

Description

Apache Log4j2 versions 2.0-alpha1 through 2.16.0 (excluding 2.12.3 and 2.3.1) did not protect from uncontrolled recursion from self-referential lookups. This allows an attacker with control over Thread Context Map data to cause a denial of service when a crafted string is interpreted. This issue was fixed in Log4j 2.17.0, 2.12.3, and 2.3.1.

Technical details

Published
2021-12-18

Frequently asked questions

What is CVE-2021-45105?

Apache Log4j2 versions 2.0-alpha1 through 2.16.0 (excluding 2.12.3 and 2.3.1) did not protect from uncontrolled recursion from self-referential lookups. This allows an attacker with control over Thread Context Map data to cause a denial of service when a crafted string is interpreted. This issue was fixed in Log4j 2.17.0, 2.12.3, and 2.3.1.

Is CVE-2021-45105 actively exploited?

Active exploitation of CVE-2021-45105 has not been confirmed. Its EPSS score was 100.0% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-45105?

CVE-2021-45105 has a CVSS v3 base score of 5.9 (MEDIUM severity).

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