CVE-2021-33037
MediumHTTP Request Smuggling in Apache Tomcat
Published Aug 13, 2021 · Updated Oct 10, 2026 · Also known as BIT-tomcat-2021-33037, DEBIAN-CVE-2021-33037, GHSA-4vww-mc66-62m6, UBUNTU-CVE-2021-33037
Key Facts
Patch immediately- CVE-2021-33037 is a medium-severity vulnerability (CVSS 5.3 v3.1) affecting Tomcat (Apache), Tomee (Apache), Epolicy Orchestrator (Mcafee) and 22 more products.
- It is not listed in any known-exploited vulnerabilities catalog. No public exploit code is known.
- EPSS estimates a 75% probability of exploitation in the next 30 days.
- Fixed versions are available, including Tomcat <=8.5.66, Tomcat 8.5.60-3.ph1, Tomcat 8.5.60-3.ph2.
- Brandefense priority: patch immediately, because it is very likely to be exploited soon.
CVSS v3.1
5.3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
EPSS (30-day exploit likelihood)
75%
Higher than 99.4% of all scored CVEs
Exploited in the wild
No known
Not in a known-exploited catalog
Public exploit code
None known
Get the full CVE-2021-33037 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
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 Products
325 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| TomcatApache | >= 8.5.0 | 8.5.66 |
| TomeeApache | 8.0.6 | n/a |
| Epolicy OrchestratorMcafee | 5.10.0, 5.10.0-update_1, 5.10.0-update_10, 5.10.0-update_2, 5.10.0-update_3, 5.10.0-update_4, 5.10.0-update_5, 5.10.0-update_6 | 5.10.0 |
| Agile PlmOracle | 9.3.6 | n/a |
| Agile Product Lifecycle ManagementOracle | 9.3.6 | n/a |
Patched Releases
Tomcat
<=8.5.66, 8.5.60-3.ph1, 8.5.60-3.ph2, 8.5.60-3.ph3, 8.5.68-1.ph4, 10.0.7, 8.5.67, 9.0.115-3.160.1, 9.0.36-13.1, 9.0.36-3.71.1, 9.0.36-3.84.1, 9.0.36-4.63.1, 9.0.36-lp152.2.25.1, 9.0.43-2.1, 9.0.47
tomcat-webapps
8.5.68-1.ph4, 9.0.115-3.160.1, 9.0.36-13.1, 9.0.36-3.71.1, 9.0.36-3.84.1, 9.0.36-4.63.1, 9.0.36-lp152.2.25.1, 9.0.43-2.1
javapackages-tools
2.0.1-13.1
jws5-tomcat
0:9.0.50-3.redhat_00004.1.el7jws, 0:9.0.50-3.redhat_00004.1.el8jws
jws5-tomcat-native
0:1.2.30-3.redhat_3.el7jws, 0:1.2.30-3.redhat_3.el8jws
jws5-tomcat-vault
0:1.1.8-4.Final_redhat_00004.1.el7jws, 0:1.1.8-4.Final_redhat_00004.1.el8jws
Epolicy Orchestrator
5.10.0
Communications Diameter Signaling Router
<=8.5.0.2
Communications Session Report Manager
<=8.2.4.0
Communications Session Route Manager
<=8.2.4
Graph Server And Client
21.4
Mysql Enterprise Monitor
<=8.0.25
org.apache.tomcat:tomcat
10.0.7, 8.5.68, 9.0.48
tomcat-admin-webapps
9.0.115-3.160.1, 9.0.36-13.1, 9.0.36-3.71.1, 9.0.36-3.84.1, 9.0.36-4.63.1, 9.0.36-lp152.2.25.1, 9.0.43-2.1
tomcat-docs-webapp
9.0.115-3.160.1, 9.0.36-13.1, 9.0.36-3.71.1, 9.0.36-lp152.2.25.1, 9.0.43-2.1
tomcat-el-3_0-api
9.0.115-3.160.1, 9.0.36-13.1, 9.0.36-3.71.1, 9.0.36-3.84.1, 9.0.36-4.63.1, 9.0.36-lp152.2.25.1, 9.0.43-2.1
tomcat-embed
9.0.36-13.1, 9.0.36-lp152.2.25.1, 9.0.43-2.1
tomcat-javadoc
9.0.115-3.160.1, 9.0.36-13.1, 9.0.36-3.71.1, 9.0.36-lp152.2.25.1, 9.0.43-2.1
tomcat-jsp-2_3-api
9.0.115-3.160.1, 9.0.36-13.1, 9.0.36-3.71.1, 9.0.36-3.84.1, 9.0.36-4.63.1, 9.0.36-lp152.2.25.1, 9.0.43-2.1
tomcat-jsvc
9.0.36-13.1, 9.0.36-lp152.2.25.1, 9.0.43-2.1
tomcat-lib
9.0.115-3.160.1, 9.0.36-13.1, 9.0.36-3.71.1, 9.0.36-3.84.1, 9.0.36-4.63.1, 9.0.36-lp152.2.25.1, 9.0.43-2.1
tomcat-servlet-4_0-api
9.0.115-3.160.1, 9.0.36-13.1, 9.0.36-3.71.1, 9.0.36-3.84.1, 9.0.36-4.63.1, 9.0.36-lp152.2.25.1, 9.0.43-2.1
tomcat10
10.1.14-1.1
tomcat10-admin-webapps
10.1.14-1.1
tomcat10-doc
10.1.14-1.1
Timeline
Publicly disclosed
Aug 13, 2021
Last updated
Oct 10, 2026
Weakness Type
- CWE-444 Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
References
- advisoryhttp://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-11022
- advisoryhttp://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-11023
- advisoryhttp://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-14782
- advisoryhttp://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29682
- advisoryhttp://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29683
FAQ
Common Questions.
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.
Affected: Tomcat (Apache) versions >= 8.5.0; Tomee (Apache) versions 8.0.6; Epolicy Orchestrator (Mcafee) versions 5.10.0, 5.10.0-update_1, 5.10.0-update_10, 5.10.0-update_2, 5.10.0-update_3, 5.10.0-update_4, 5.10.0-update_5, 5.10.0-update_6, among others. The full list is in the CVE brief.
It is not listed in any known-exploited vulnerabilities catalog.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
No public exploit code is known.
Fixed versions are available, including Tomcat <=8.5.66, Tomcat 8.5.60-3.ph1, Tomcat 8.5.60-3.ph2.
Brandefense priority: patch immediately, because it is very likely to be exploited soon.
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