How severe is CVE-2021-43980?

CVE-2021-43980 has a CVSS 3.x base score of 3.7, rated low severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2021-43980 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (75th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-43980?

CVE-2021-43980 primarily affects Apache Tomcat. In total, 15 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-43980?

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

When was CVE-2021-43980 published?

CVE-2021-43980 was published on 2022-09-28 and last updated on 2026-06-17.

CVE-2021-43980

CVE-2021-43980 is a low-severity vulnerability in Apache Tomcat with a CVSS 3.x base score of 3.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-362.

Key facts

Severity: Low (CVSS 3.x base score 3.7)
EPSS exploit prediction: 2% (75th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-362
Affected product: Apache Tomcat
Published: 2022-09-28
Last modified: 2026-06-17

Description

The simplified implementation of blocking reads and writes introduced in Tomcat 10 and back-ported to Tomcat 9.0.47 onwards exposed a long standing (but extremely hard to trigger) concurrency bug in Apache Tomcat 10.1.0 to 10.1.0-M12, 10.0.0-M1 to 10.0.18, 9.0.0-M1 to 9.0.60 and 8.5.0 to 8.5.77 that could cause client connections to share an Http11Processor instance resulting in responses, or part responses, to be received by the wrong client.

Frequently asked questions

What is CVE-2021-43980?: The simplified implementation of blocking reads and writes introduced in Tomcat 10 and back-ported to Tomcat 9.0.47 onwards exposed a long standing (but extremely hard to trigger) concurrency bug in Apache Tomcat 10.1.0 to 10.1.0-M12, 10.0.0-M1 to 10.0.18, 9.0.0-M1 to 9.0.60 and 8.5.0 to 8.5.77 that could cause client connections to share an Http11Processor instance resulting in responses, or part responses, to be received by the wrong client.
How severe is CVE-2021-43980?: CVE-2021-43980 has a CVSS 3.x base score of 3.7, rated low severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2021-43980 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (75th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43980?: CVE-2021-43980 primarily affects Apache Tomcat. In total, 15 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-43980?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-43980 published?: CVE-2021-43980 was published on 2022-09-28 and last updated on 2026-06-17.

References

Affected products (15)

cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:*
cpe:2.3:a:apache:tomcat:10.1.0:milestone1:*:*:*:*:*:*
cpe:2.3:a:apache:tomcat:10.1.0:milestone10:*:*:*:*:*:*
cpe:2.3:a:apache:tomcat:10.1.0:milestone11:*:*:*:*:*:*
cpe:2.3:a:apache:tomcat:10.1.0:milestone12:*:*:*:*:*:*
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:apache:tomcat:10.1.0:milestone6:*:*:*:*:*:*
cpe:2.3:a:apache:tomcat:10.1.0:milestone7:*:*:*:*:*:*
cpe:2.3:a:apache:tomcat:10.1.0:milestone8:*:*:*:*:*:*
cpe:2.3:a:apache:tomcat:10.1.0:milestone9:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*

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