How severe is CVE-2021-42340?

CVE-2021-42340 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-42340 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 11% (95th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-42340?

CVE-2021-42340 primarily affects Apache Tomcat. In total, 35 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-42340?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-42340 published?

CVE-2021-42340 was published on 2021-10-14 and last updated on 2026-06-17.

CVE-2021-42340

CVE-2021-42340 is a high-severity vulnerability in Apache Tomcat with a CVSS 3.x base score of 7.5. Its EPSS exploit-prediction score of 11% places it in the 95th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-772.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 11% (95th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-772
Affected product: Apache Tomcat
Published: 2021-10-14
Last modified: 2026-06-17

Description

The fix for bug 63362 present in Apache Tomcat 10.1.0-M1 to 10.1.0-M5, 10.0.0-M1 to 10.0.11, 9.0.40 to 9.0.53 and 8.5.60 to 8.5.71 introduced a memory leak. The object introduced to collect metrics for HTTP upgrade connections was not released for WebSocket connections once the connection was closed. This created a memory leak that, over time, could lead to a denial of service via an OutOfMemoryError.

Frequently asked questions

What is CVE-2021-42340?: The fix for bug 63362 present in Apache Tomcat 10.1.0-M1 to 10.1.0-M5, 10.0.0-M1 to 10.0.11, 9.0.40 to 9.0.53 and 8.5.60 to 8.5.71 introduced a memory leak. The object introduced to collect metrics for HTTP upgrade connections was not released for WebSocket connections once the connection was closed. This created a memory leak that, over time, could lead to a denial of service via an OutOfMemoryError.
How severe is CVE-2021-42340?: CVE-2021-42340 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-42340 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 11% (95th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-42340?: CVE-2021-42340 primarily affects Apache Tomcat. In total, 35 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-42340?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-42340 published?: CVE-2021-42340 was published on 2021-10-14 and last updated on 2026-06-17.

References

Affected products (35)

cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:*
cpe:2.3:a:apache:tomcat:10.0.0:milestone10:*:*:*:*:*:*
cpe:2.3:a:apache:tomcat:10.1.0:milestone1:*:*:*:*:*:*
cpe:2.3:a:apache:tomcat:10.1.0:milestone2:*:*:*:*:*:*
cpe:2.3:a:apache:tomcat:10.1.0:milestone3:*:*:*:*:*:*
cpe:2.3:a:apache:tomcat:10.1.0:milestone4:*:*:*:*:*:*
cpe:2.3:a:apache:tomcat:10.1.0:milestone5:*:*:*:*:*:*
cpe:2.3:a:netapp:hci:-:*:*:*:*:*:*:*
cpe:2.3:a:netapp:management_services_for_element_software:-:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:agile_engineering_data_management:6.2.1.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:big_data_spatial_and_graph:*:*:*:*:*:*:*:*
cpe:2.3:a:oracle:communications_diameter_signaling_router:*:*:*:*:*:*:*:*
cpe:2.3:a:oracle:hospitality_cruise_shipboard_property_management_system:20.1.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:managed_file_transfer:12.2.1.3.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:managed_file_transfer:12.2.1.4.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:middleware_common_libraries_and_tools:12.2.1.4.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:payment_interface:19.1:*:*:*:*:*:*:*
cpe:2.3:a:oracle:payment_interface:20.3:*:*:*:*:*:*:*
cpe:2.3:a:oracle:retail_customer_insights:15.0.2:*:*:*:*:*:*:*
cpe:2.3:a:oracle:retail_customer_insights:16.0.2:*:*:*:*:*:*:*
cpe:2.3:a:oracle:retail_data_extractor_for_merchandising:15.0.2:*:*:*:*:*:*:*
cpe:2.3:a:oracle:retail_data_extractor_for_merchandising:16.0.2:*:*:*:*:*:*:*
cpe:2.3:a:oracle:retail_eftlink:21.0.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:retail_financial_integration:16.0.1:*:*:*:*:*:*:*
cpe:2.3:a:oracle:retail_financial_integration:19.0.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:retail_store_inventory_management:14.0.4.13:*:*:*:*:*:*:*
cpe:2.3:a:oracle:retail_store_inventory_management:14.1.3.5:*:*:*:*:*:*:*
cpe:2.3:a:oracle:retail_store_inventory_management:14.1.3.14:*:*:*:*:*:*:*
cpe:2.3:a:oracle:retail_store_inventory_management:15.0.3.3:*:*:*:*:*:*:*
cpe:2.3:a:oracle:retail_store_inventory_management:15.0.3.8:*:*:*:*:*:*:*
cpe:2.3:a:oracle:retail_store_inventory_management:16.0.3.7:*:*:*:*:*:*:*
cpe:2.3:a:oracle:sd-wan_edge:9.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:sd-wan_edge:9.1:*:*:*:*:*:*:*
cpe:2.3:a:oracle:taleo_platform:*:*:*:*:*:*:*:*

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