Incorrect Transfer-Encoding handling with HTTP/1.0

Summary

Apache Tomcat 10.0.0-M1 to 10.0.6, 9.0.0.M1 to 9.0.46 and 8.5.0 to 8.5.66 did not correctly parse the HTTP transfer-encoding request header in some circumstances leading to the possibility to request smuggling when used with a reverse proxy. Specifically: - Tomcat incorrectly ignored the transfer encoding header if the client declared it would only accept an HTTP/1.0 response; - Tomcat honoured the identify encoding; and - Tomcat did not ensure that, if present, the chunked encoding was the final encoding.

Timeline

1. Jul 12, 2021, 2:55 PM UTCCVE published
2. Oct 8, 2026, 9:05 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: partial

3. Oct 8, 2026, 9:13 PM UTCRecord last updated
4. Oct 22, 2026EPSS reached 10%

   FIRST estimates at least a 10% chance of exploitation in the next 30 days

Affected versions

• Apache Software Foundation Apache Tomcat

  Apache Tomcat 10 10.0.0-M1 to 10.0.6, Apache Tomcat 9 9.0.0.M1 to 9.0.46, Apache Tomcat 8 8.5.0 to 8.5.66

• tomcatBitnami

  From 8.5.0 · fixed in 8.5.67; From 9.0.0 · fixed in 9.0.47; From 10.0.0 · fixed in 10.0.7

• org.apache.tomcat:tomcatMaven

  From 10.0.0-M1 · fixed in 10.0.7

• org.apache.tomcat:tomcatMaven

  From 9.0.0-M1 · fixed in 9.0.48

• org.apache.tomcat:tomcatMaven

  From 8.5.0 · fixed in 8.5.68

References 16