CVE-2021-43980

Name	CVE-2021-43980
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.
Source	CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
References	DLA-3160-1, DSA-5265-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
tomcat9 (PTS)	buster	9.0.31-1~deb10u6	vulnerable
	buster (security)	9.0.31-1~deb10u12	fixed
	bullseye	9.0.43-2~deb11u9	fixed
	bullseye (security)	9.0.43-2~deb11u10	fixed
	sid, trixie, bookworm	9.0.70-2	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Origin
tomcat8	source	(unstable)	(unfixed)
tomcat9	source	buster	9.0.31-1~deb10u7	DLA-3160-1
tomcat9	source	bullseye	9.0.43-2~deb11u4	DSA-5265-1
tomcat9	source	(unstable)	9.0.62-1

Notes

https://lists.apache.org/thread/3jjqbsp6j88b198x5rmg99b1qr8ht3g3
https://github.com/apache/tomcat/commit/170e0f792bd18ff031677890ba2fe50eb7a376c1 (9.0.61)
https://github.com/apache/tomcat/commit/4a00b0c0890538b9d3107eef8f2e0afadd119beb (8.5.78)