CVE-2026-77756: apache software foundation apache tomcat HTTP Request/Response Smuggling

Vulnerability summary

CVE-2026-77756 is a low (CVSS 3.7) HTTP Request/Response Smuggling vulnerability in apache software foundation apache tomcat. EPSS estimates a 0.26% chance of exploitation in the next 30 days, higher than 16.1% of scored vulnerabilities.

Timeline

1. 23-09-2026
   PublishedVulnerability first disclosed.
2. 23-09-2026
   Last modifiedVulnerability information updated.

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.

• CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.