--- title: "CVE-2021-33037: Incorrect Transfer-Encoding handling… | CubePath" 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…" language: en source: https://cubepath.com/security/cve/CVE-2021-33037 --- # CVE-2021-33037: Incorrect Transfer-Encoding handling… | CubePath ## 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](https://cubepath.com/security/cve/legal) for the CVE license. [View the record on cve.org](https://www.cve.org/CVERecord?id=CVE-2021-33037) ## 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](https://cubepath.com/security/cve/legal) for the CWE license. - [CWE-444](https://cwe.mitre.org/data/definitions/444.html) Inconsistent 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. - [lists.apache.org/thread.html/r612a79269b0d5e5780c62dfd34286…](https://lists.apache.org/thread.html/r612a79269b0d5e5780c62dfd34286a8037232fec0bc6f1a7e60c9381%40%3Cannounce.tomcat.apache.org%3E) - [oracle.com//security-alerts/cpujul2021.html](https://www.oracle.com//security-alerts/cpujul2021.html) - [\[tomee-commits\] 20210728 \[jira\] \[Created\] (TOMEE-3778) Update embedded Tomcat to 9.0.48 or later to address CVE-2021-33037](https://lists.apache.org/thread.html/r40f921575aee8d7d34e53182f862c45cbb8f3d898c9d4e865c2ec262%40%3Ccommits.tomee.apache.org%3E) (lists.apache.org) mailing-list - [\[tomee-commits\] 20210728 \[jira\] \[Commented\] (TOMEE-3778) Update embedded Tomcat to 9.0.48 or later to address CVE-2021-33037](https://lists.apache.org/thread.html/re01e7e93154e8bdf78a11a23f9686427bd3d51fc6e12c508645567b7%40%3Ccommits.tomee.apache.org%3E) (lists.apache.org) mailing-list - [\[debian-lts-announce\] 20210805 \[SECURITY\] \[DLA 2733-1\] tomcat8 security update](https://lists.debian.org/debian-lts-announce/2021/08/msg00009.html) (lists.debian.org) mailing-list - [DSA-4952](https://www.debian.org/security/2021/dsa-4952) (debian.org) vendor-advisory - [\[tomee-commits\] 20210830 \[jira\] \[Commented\] (TOMEE-3778) Update embedded Tomcat to 9.0.48 or later to address CVE-2021-33037](https://lists.apache.org/thread.html/rd0dfea39829bc0606c936a16f6fca338127c86c0a1083970b45ac8d2%40%3Ccommits.tomee.apache.org%3E) (lists.apache.org) mailing-list - [\[tomee-commits\] 20210913 \[jira\] \[Commented\] (TOMEE-3778) Update embedded Tomcat to 9.0.48 or later to address CVE-2021-33037](https://lists.apache.org/thread.html/r290aee55b72811fd19e75ac80f6143716c079170c5671b96932ed44b%40%3Ccommits.tomee.apache.org%3E) (lists.apache.org) mailing-list - [\[tomee-commits\] 20210914 \[jira\] \[Commented\] (TOMEE-3778) Update embedded Tomcat to 9.0.48 or later to address CVE-2021-33037](https://lists.apache.org/thread.html/rf1b54fd3f52f998ca4829159a88cc4c23d6cef5c6447d00948e75c97%40%3Ccommits.tomee.apache.org%3E) (lists.apache.org) mailing-list - [\[tomee-commits\] 20210916 \[jira\] \[Resolved\] (TOMEE-3778) Update embedded Tomcat to 9.0.48 or later to address CVE-2021-33037](https://lists.apache.org/thread.html/rc6ef52453bb996a98cb45442871a1db56b7c349939e45d829bf9ae37%40%3Ccommits.tomee.apache.org%3E) (lists.apache.org) mailing-list - [oracle.com/security-alerts/cpuoct2021.html](https://www.oracle.com/security-alerts/cpuoct2021.html) - [security.netapp.com/advisory/ntap-20210827-0007](https://security.netapp.com/advisory/ntap-20210827-0007/) - [kc.mcafee.com/corporate/index?page=content&id=SB10366](https://kc.mcafee.com/corporate/index?page=content&id=SB10366) - [oracle.com/security-alerts/cpujan2022.html](https://www.oracle.com/security-alerts/cpujan2022.html) - [oracle.com/security-alerts/cpuapr2022.html](https://www.oracle.com/security-alerts/cpuapr2022.html) - [GLSA-202208-34](https://security.gentoo.org/glsa/202208-34) (security.gentoo.org) vendor-advisory ## Timeline 1. ID reserved May 17, 2021 2. Record published Jul 12, 2021 3. Record last updated Oct 8, 2026 ## Look up another CVE ## About CubePath CubePath is a cloud provider with data centers in Europe and the United States. It offers VPS, bare metal servers and DDoS protection. [Cloud VPS](https://cubepath.com/vps) [DDoS protection](https://cubepath.com/ddos-protection) 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, 20:04 UTC. [Sources and licenses](https://cubepath.com/security/cve/legal)