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Vulnerability record · CVE-2021-43980 · published 28 September 2022

CVE-2021-43980: Apache tomcat race condition vulnerability

Apache · Tomcat

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.

3.7 CVSS 3.1 Low EPSS 2.4% · top 16.9% CWE-362 · Race condition
3.7CVSS 3.1 base score
2.4%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
8References
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://www.openwall.com/lists/oss-security/2022/09/28/1 Mailing ListThird Party Advisory
https://lists.apache.org/thread/3jjqbsp6j88b198x5rmg99b1qr8ht3g3 Mailing ListVendor Advisory
https://lists.debian.org/debian-lts-announce/2022/10/msg00029.html Mailing ListThird Party Advisory
https://www.debian.org/security/2022/dsa-5265 Third Party Advisory
http://www.openwall.com/lists/oss-security/2022/09/28/1 Mailing ListThird Party Advisory
https://lists.apache.org/thread/3jjqbsp6j88b198x5rmg99b1qr8ht3g3 Mailing ListVendor Advisory
https://lists.debian.org/debian-lts-announce/2022/10/msg00029.html Mailing ListThird Party Advisory
https://www.debian.org/security/2022/dsa-5265 Third Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-43980), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.