CVE-2021-45105

CVE-2021-45105 is a medium-severity vulnerability in Apache Log4j with a CVSS 3.x base score of 5.9. Its EPSS exploit-prediction score of 100% places it in the 100th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-20.

Key facts

• Severity: Medium (CVSS 3.x base score 5.9)
• CVSS v2: 4.3
• EPSS exploit prediction: 100% (100th percentile)
• Actively exploited: Not listed in CISA KEV
• Weakness: CWE-20
• Affected product: Apache Log4j
• Published: 2021-12-18
• Last modified: 2026-06-17

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.

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.

How severe is CVE-2021-45105?

CVE-2021-45105 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-45105 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 100% (100th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-45105?

CVE-2021-45105 primarily affects Apache Log4j. In total, 200 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-45105?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-45105 published?

CVE-2021-45105 was published on 2021-12-18 and last updated on 2026-06-17.

References

• http://www.openwall.com/lists/oss-security/2021/12/19/1
• https://cert-portal.siemens.com/productcert/pdf/ssa-479842.pdf
• https://cert-portal.siemens.com/productcert/pdf/ssa-501673.pdf
• https://logging.apache.org/log4j/2.x/security.html
• https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0032
• https://security.netapp.com/advisory/ntap-20211218-0001/
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-log4j-qRuKNEbd
• https://www.debian.org/security/2021/dsa-5024
• https://www.kb.cert.org/vuls/id/930724
• https://www.oracle.com/security-alerts/cpuapr2022.html
• https://www.oracle.com/security-alerts/cpujan2022.html
• https://www.oracle.com/security-alerts/cpujul2022.html
• https://www.zerodayinitiative.com/advisories/ZDI-21-1541/

Affected products (200)

• cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*
• cpe:2.3:a:netapp:cloud_manager:-:*:*:*:*:*:*:*
• cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
• cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
• cpe:2.3:a:sonicwall:email_security:*:*:*:*:*:*:*:*
• cpe:2.3:a:sonicwall:network_security_manager:*:*:*:*:on-premises:*:*:*
• cpe:2.3:a:sonicwall:network_security_manager:*:*:*:*:saas:*:*:*
• cpe:2.3:a:sonicwall:web_application_firewall:*:*:*:*:*:*:*:*
• cpe:2.3:o:sonicwall:6bk1602-0aa12-0tp0_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:sonicwall:6bk1602-0aa22-0tp0_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:sonicwall:6bk1602-0aa32-0tp0_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:sonicwall:6bk1602-0aa42-0tp0_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:sonicwall:6bk1602-0aa52-0tp0_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:agile_engineering_data_management:6.2.1.0:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:agile_plm:9.3.6:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:agile_plm_mcad_connector:3.6:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:autovue_for_agile_product_lifecycle_management:21.0.2:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:banking_deposits_and_lines_of_credit_servicing:2.12.0:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:banking_enterprise_default_management:2.7.1:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:banking_enterprise_default_management:2.12.0:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:banking_loans_servicing:2.12.0:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:banking_party_management:2.7.0:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:banking_payments:14.5:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:banking_platform:2.6.2:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:banking_platform:2.7.1:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:banking_platform:2.12.0:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:banking_trade_finance:14.5:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:banking_treasury_management:14.5:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:business_intelligence:5.5.0.0.0:*:*:*:enterprise:*:*:*
• cpe:2.3:a:oracle:communications_asap:7.3:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:communications_billing_and_revenue_management:12.0.0.4:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:communications_billing_and_revenue_management:12.0.0.5:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:communications_cloud_native_core_console:1.9.0:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:communications_cloud_native_core_network_function_cloud_native_environment:1.10.0:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:communications_cloud_native_core_network_repository_function:1.15.0:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:communications_cloud_native_core_network_repository_function:1.15.1:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:communications_cloud_native_core_network_slice_selection_function:1.8.0:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:communications_cloud_native_core_policy:1.15.0:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:communications_cloud_native_core_security_edge_protection_proxy:1.7.0:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:communications_cloud_native_core_service_communication_proxy:1.15.0:*:*:*:*:*:*:*

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• CVE-2019-17571 — Critical (CVSS 9.8): Included in Log4j 1.2 is a SocketServer class that is vulnerable to deserialization of untrusted data which can be…
• CVE-2017-5645 — Critical (CVSS 9.8): In Apache Log4j 2.x before 2.8.2, when using the TCP socket server or UDP socket server to receive serialized log…
• CVE-2021-45046 — Critical (CVSS 9.0): It was found that the fix to address CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete in certain non-default…

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