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CVE-2021-33037

61
FAUCET Score

CVE-2021-33037 is a medium-severity request smuggling vulnerability affecting Apache Tomcat versions 10.0.0-M1 to 10.0.6, 9.0.0.M1 to 9.0.46, and 8.5.0 to 8.5.66, as well as products like Debian, McAfee, and Oracle that incorporate these Tomcat versions. The vulnerability arises from incorrect parsing of the HTTP transfer-encoding header, particularly when used with a reverse proxy, allowing for potential request smuggling attacks. With a CVSS score of 5.3, it has a low attack complexity and requires no user interaction, but its impact is limited to integrity. There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage, indicating a low current threat level.

Impacted Technologies

VendorProductVersion(s)CPE
>= 8.5.0, <= 8.5.66CPE matchmatch criteria
cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:*
> 9.0.0, <= 9.0.46CPE matchmatch criteria
cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:*
> 10.0.0, <= 10.0.6CPE matchmatch criteria
cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:*
8.0.6CPE matchmatch criteria
cpe:2.3:a:apache:tomee:8.0.6:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.3MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
75.35%
Probability of exploitation in next 30 days
EPSS Percentile
99.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.7535 is in the 100th percentile among its peer group of 23,723 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (13)

mavenpatch availablevia ghsa
Product: org.apache.tomcat:tomcatFixed in: 8.5.68
mavenpatch availablevia ghsa
Product: org.apache.tomcat:tomcatFixed in: 10.0.7
mavenpatch availablevia ghsa
Product: org.apache.tomcat:tomcatFixed in: 9.0.48
oraclepatch availablevia nvd_reference
View patch
redhatpatch availablevia redhat_api
Product: Red Hat JBoss Web Server 5.6 on RHEL 7Fixed in: jws5-tomcat-native-0:1.2.30-3.redhat_3.el7jws
View patch
redhatpatch availablevia redhat_api
Product: Red Hat JBoss Web Server 5.6 on RHEL 7Fixed in: jws5-tomcat-vault-0:1.1.8-4.Final_redhat_00004.1.el7jws
View patch
redhatpatch availablevia redhat_api
Product: Red Hat JBoss Web Server 5.6 on RHEL 8Fixed in: jws5-tomcat-0:9.0.50-3.redhat_00004.1.el8jws
View patch
redhatpatch availablevia redhat_api
Product: Red Hat JBoss Web Server 5.6 on RHEL 8Fixed in: jws5-tomcat-native-0:1.2.30-3.redhat_3.el8jws
View patch
redhatpatch availablevia redhat_api
Product: Red Hat JBoss Web Server 5.6 on RHEL 8Fixed in: jws5-tomcat-vault-0:1.1.8-4.Final_redhat_00004.1.el8jws
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Support for Spring Boot 2.5.10Fixed in: tomcat
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Fuse 7.11Fixed in: tomcat
View patch
redhatpatch availablevia redhat_api
Product: Red Hat JBoss Web Server 5Fixed in: tomcat
View patch
redhatpatch availablevia redhat_api
Product: Red Hat JBoss Web Server 5.6 on RHEL 7Fixed in: jws5-tomcat-0:9.0.50-3.redhat_00004.1.el7jws
View patch

Vendor Advisories (2)

mavenGHSA-4vww-mc66-62m6medium

HTTP Request Smuggling in Apache Tomcat

Aug 13, 2021
redhatCVE-2021-33037Moderate

tomcat: HTTP request smuggling when used with a reverse proxy

Jul 12, 2021

References

kc.mcafee.com / corporate/index
Third Party Advisory
lists.apache.org / thread.html/r290aee55b72811fd19e75ac80f6143716c079170c5671b96932ed44b%40%3Ccommits.tomee.apache.org%3E
lists.apache.org / thread.html/r40f921575aee8d7d34e53182f862c45cbb8f3d898c9d4e865c2ec262%40%3Ccommits.tomee.apache.org%3E
lists.apache.org / thread.html/r612a79269b0d5e5780c62dfd34286a8037232fec0bc6f1a7e60c9381%40%3Cannounce.tomcat.apache.org%3E
Mailing ListVendor Advisory
lists.apache.org / thread.html/rc6ef52453bb996a98cb45442871a1db56b7c349939e45d829bf9ae37%40%3Ccommits.tomee.apache.org%3E
lists.apache.org / thread.html/rd0dfea39829bc0606c936a16f6fca338127c86c0a1083970b45ac8d2%40%3Ccommits.tomee.apache.org%3E
lists.apache.org / thread.html/re01e7e93154e8bdf78a11a23f9686427bd3d51fc6e12c508645567b7%40%3Ccommits.tomee.apache.org%3E
lists.apache.org / thread.html/rf1b54fd3f52f998ca4829159a88cc4c23d6cef5c6447d00948e75c97%40%3Ccommits.tomee.apache.org%3E
lists.debian.org / debian-lts-announce/2021/08/msg00009.html
Mailing ListThird Party Advisory
security.gentoo.org / glsa/202208-34
Third Party Advisory
security.netapp.com / advisory/ntap-20210827-0007
Third Party Advisory
debian.org / security/2021/dsa-4952
Third Party Advisory
oracle.com / security-alerts/cpuapr2022.html
PatchThird Party Advisory
oracle.com / security-alerts/cpujan2022.html
PatchThird Party Advisory
oracle.com / /security-alerts/cpujul2021.html
PatchThird Party Advisory
oracle.com / security-alerts/cpuoct2021.html
PatchThird Party Advisory