Reference page — cumulative record through Monday, October 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2021-33037

CVE-2021-33037MEDIUM

Apache Software Foundation Apache Tomcat — Incorrect Transfer-Encoding handling with HTTP/1.0

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   N  U  N  L  N    5.3   .7467   99.5     —

AFFECTED
  Product        Versions                                Fixed
  Apache Tomcat  Apache Tomcat 10 10.0.0-M1 to 10.0.6 –  —

TIMELINE
  May 17  Reserved by apache
  Jul 12  Published (CNA: apache)
  Oct 8   ENRICHED — CVE-2021-33037 (Apache Software Foundation Apache Tomcat). Received CVSS 5.3 and CPE data from NVD.

CWE-444 · CNA: apache · CVSS v3.1 · 16 references · NVD status: Modified

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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
May 17, 2021	Reserved	Reserved by apache
July 12, 2021	Published	Published (CNA: apache)
October 8, 2026	ENRICHED	ENRICHED — CVE-2021-33037 (Apache Software Foundation Apache Tomcat). Received CVSS 5.3 and CPE data from NVD.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
Apache Software Foundation	Apache Tomcat	—	Apache Tomcat 10 10.0.0-M1 to 10.0.6	—

Weaknesses

CWE-444

References (16)

https://kc.mcafee.com/corporate/index?page=content&id=SB10366 [Third Party Advisory]
https://lists.apache.org/thread.html/r290aee55b72811fd19e75ac80f6143716c079170c5671b96932ed44b%40%3Ccommits.tomee.apache.org%3E
https://lists.apache.org/thread.html/r40f921575aee8d7d34e53182f862c45cbb8f3d898c9d4e865c2ec262%40%3Ccommits.tomee.apache.org%3E
https://lists.apache.org/thread.html/r612a79269b0d5e5780c62dfd34286a8037232fec0bc6f1a7e60c9381%40%3Cannounce.tomcat.apache.org%3E [Mailing List, Vendor Advisory]
https://lists.apache.org/thread.html/rc6ef52453bb996a98cb45442871a1db56b7c349939e45d829bf9ae37%40%3Ccommits.tomee.apache.org%3E
https://lists.apache.org/thread.html/rd0dfea39829bc0606c936a16f6fca338127c86c0a1083970b45ac8d2%40%3Ccommits.tomee.apache.org%3E
https://lists.apache.org/thread.html/re01e7e93154e8bdf78a11a23f9686427bd3d51fc6e12c508645567b7%40%3Ccommits.tomee.apache.org%3E
https://lists.apache.org/thread.html/rf1b54fd3f52f998ca4829159a88cc4c23d6cef5c6447d00948e75c97%40%3Ccommits.tomee.apache.org%3E
https://lists.debian.org/debian-lts-announce/2021/08/msg00009.html [Mailing List, Third Party Advisory]
https://security.gentoo.org/glsa/202208-34 [Third Party Advisory]
https://security.netapp.com/advisory/ntap-20210827-0007/ [Third Party Advisory]
https://www.debian.org/security/2021/dsa-4952 [Third Party Advisory]
https://www.oracle.com//security-alerts/cpujul2021.html [Patch, Third Party Advisory]
https://www.oracle.com/security-alerts/cpuapr2022.html [Patch, Third Party Advisory]
https://www.oracle.com/security-alerts/cpujan2022.html [Patch, Third Party Advisory]
https://www.oracle.com/security-alerts/cpuoct2021.html [Patch, Third Party Advisory]

Authoritative record: CVE-2021-33037 at cve.org

Vendors: apache

Weaknesses: CWE-444

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2021-33037 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Monday, October 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.