CVE-2021-43980: Apache Tomcat: Information disclosure

[Mark Thomas <markt () apache org>]

Severity: important

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.

Credit:

Thanks to Adam Thomas, Richard Hernandez and Ryan Schmitt for 
discovering the issue and working with the Tomcat security team to 
identify the root cause and appropriate fix.

References:

https://lists.apache.org/thread/3jjqbsp6j88b198x5rmg99b1qr8ht3g3