CVE-2021-33037

Incorrect Transfer-Encoding handling with HTTP/1.0

MEDIUM
5.3
CVSS Score
Published: July 12, 2021 at 02:55 PM UTC
Updated: October 8, 2026 at 10:17 PM UTC
22 products affected across 4 vendorsDebian LinuxTomcatAgile Product Lifecycle Management

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Severity
MEDIUM5.3
Exploit prediction
EPSS 75%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

8.5.0 ≤ v ≤ 8.5.6610.0.0 < v ≤ 10.0.69.0.0 < v ≤ 9.0.46*Apache Tomcat 10 10.0.0-M1 to 10.0.6Apache Tomcat 8 8.5.0 to 8.5.66Apache Tomcat 9 9.0.0.M1 to 9.0.46

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-444

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