CVE-2021-43980

Name: CVE-2021-43980
Creator: NVD / NIST
Published: 2022-09-28T14:15:09.88+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

LOWCVSS 3.7/10EPSS 1.75%

Last modified Jun 17, 2026

CVE-2021-43980 is a low-severity vulnerability rated 3.7/10 on the CVSS scale. 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.. EPSS estimates a 1.75% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

3.7/10

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

EPSS Probability

1.75%

74.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions	Update
Apache	Tomcat	>= 8.5.0, <= 8.5.77	—
Apache	Tomcat	>= 9.0.0, <= 9.0.60	—
Apache	Tomcat	>= 10.0.0, <= 10.0.18	—
Apache	Tomcat	10.1.0	Milestone1
Debian	Debian Linux	10.0	—
Debian	Debian Linux	11.0	—

References

http://www.openwall.com/lists/oss-security/2022/09/28/1Mailing List, Third Party Advisory
https://lists.apache.org/thread/3jjqbsp6j88b198x5rmg99b1qr8ht3g3Mailing List, Vendor Advisory
https://lists.debian.org/debian-lts-announce/2022/10/msg00029.htmlMailing List, Third Party Advisory
https://www.debian.org/security/2022/dsa-5265Third Party Advisory
http://www.openwall.com/lists/oss-security/2022/09/28/1Mailing List, Third Party Advisory
https://lists.apache.org/thread/3jjqbsp6j88b198x5rmg99b1qr8ht3g3Mailing List, Vendor Advisory
https://lists.debian.org/debian-lts-announce/2022/10/msg00029.htmlMailing List, Third Party Advisory
https://www.debian.org/security/2022/dsa-5265Third Party Advisory

Timeline

Published: Sep 28, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-43980?

How severe is CVE-2021-43980?

CVE-2021-43980 has a CVSS score of 3.7/10 (LOW severity). The EPSS model estimates a 1.75% probability of exploitation in the next 30 days.

How do I fix CVE-2021-43980?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-43980?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST