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Vulnerability · Published Sep 23, 2026 · Assigned by apache

CVE-2026-77756Apache Tomcat: Transfer-Encoding honored for HTTP/1.0 requests

Low 3.7

In plain English

A low-severity security flaw in Apache Tomcat from Apache Software Foundation. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 45% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)3.7Low
Exploit odds (30 days)0.5%top 55.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in Apache Tomcat caused by processing the transfer-encoding header for an HTTP/1.0 request may allow an attacker to cause one request from another user to fail when Tomcat is located behind a reverse proxy. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.25, from 10.1.0-M1 through 10.1.59, from 9.0.47 through 9.0.121. The following versions were EOL at the time the CVE was created but are known to be affected: from 8.5.67 through 8.5.100. Other unsupported versions may also be affected. Users are recommended to upgrade to version 11.0.26, 10.1.60 or 9.0.122, which fix the issue.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12tomcat10no fix listedDEBIAN-CVE-2026-77756
Debian:13tomcat10no fix listedDEBIAN-CVE-2026-77756
Debian:14tomcat1010.1.60-1DEBIAN-CVE-2026-77756
Debian:13tomcat11no fix listedDEBIAN-CVE-2026-77756
Debian:14tomcat11no fix listedDEBIAN-CVE-2026-77756
Debian:12tomcat99.0.70-2DEBIAN-CVE-2026-77756
Debian:13tomcat99.0.70-2DEBIAN-CVE-2026-77756
Debian:14tomcat99.0.70-2DEBIAN-CVE-2026-77756
Ubuntu:24.04:LTStomcat10no fix listedUBUNTU-CVE-2026-77756
Ubuntu:26.04:LTStomcat10no fix listedUBUNTU-CVE-2026-77756
Ubuntu:26.10tomcat10no fix listedUBUNTU-CVE-2026-77756
Ubuntu:26.04:LTStomcat11no fix listedUBUNTU-CVE-2026-77756
Ubuntu:26.10tomcat11no fix listedUBUNTU-CVE-2026-77756
Ubuntu:24.04:LTStomcat9no fix listedUBUNTU-CVE-2026-77756
Ubuntu:26.04:LTStomcat9no fix listedUBUNTU-CVE-2026-77756
Ubuntu:26.10tomcat9no fix listedUBUNTU-CVE-2026-77756

Affected products (as reported)

VendorProductVersions
Apache Software Foundation Apache Tomcat 11.0.0-M1 – through 11.0.2510.1.0-M1 – through 10.1.599.0.47 – through 9.0.1218.5.67 – through 8.5.100

Weakness: CWE-444 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

References