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CVE-2021-33037

Incorrect Transfer-Encoding handling with HTTP/1.0

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.

Official description from the CVE record, published by apache. Copyright © 1999-2026 The MITRE Corporation. See /security/cve/legal for the CVE license. View the record on cve.org

Key data

EPSS

Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days.
Score
0.74667 (74.7% probability)
Percentile
99.5%
Scores of
Nov 10, 2026
Model
v2026.06.15

CISA assessment as of Oct 8, 2026

Stakeholder-Specific Vulnerability Categorization (SSVC) decision points added by CISA.
Automatable
yes
Technical impact
partial

Weakness (CWE)

CWE catalog version 5.0.
CWE names: Copyright © 2006-2026, The MITRE Corporation. See /security/cve/legal for the CWE license.
  • CWE-444Inconsistent Interpretation of HTTP Requests

Affected products

Products listed in the CVE record, as the CNA published them.

  • Apache Tomcat

    • affected: Apache Tomcat 10 10.0.0-M1 to 10.0.6
    • affected: Apache Tomcat 9 9.0.0.M1 to 9.0.46
    • affected: Apache Tomcat 8 8.5.0 to 8.5.66

References

Links listed in the CVE record. They lead to other sites, which CubePath does not control.

Timeline

  1. ID reserved
  2. Record published
  3. Record last updated

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About CubePath

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Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 19:52 UTC. Sources and licenses