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.

How to fix CVE-2021-43980

To remediate CVE-2021-43980, upgrade the affected package to a fixed version below.

• —upgrade to 8.5.78 or later
• —upgrade to 9.0.43-2~deb11u4 or later
• —upgrade to 9.0.31-1~deb10u7 or later
• —upgrade to 9.0.43-2~deb11u4 or later
• —upgrade to 8.5.78 or later

Is CVE-2021-43980 being exploited?

Low — EPSS is 0.2%, meaning exploitation activity has not been observed at scale.

Affected packages (5)

• >= 8.5.0, < 8.5.78, >= 9.0.0, < 9.0.61, >= 10.0.0, < 10.0.19
• from 0, < 9.0.43-2~deb11u4
• from 0, < 9.0.31-1~deb10u7
• from 0, < 9.0.43-2~deb11u4
• >= 8.5.0, < 8.5.78

CVSS scores

References (14)

• ADVISORYnvd.nist.gov/vuln/detail/CVE-2021-43980
• ADVISORYsecurity-tracker.debian.org/tracker/CVE-2021-43980
• PATCHgithub.com/apache/tomcat
• WEBgithub.com/apache/tomcat/commit/170e0f792bd18ff031677890ba2fe50eb7a376c1