Inconsistent interpretation of HTTP requests in Apache Tomcat - CVE-2026-77756
Published: September 23, 2026
Vulnerability identifier: #VU151846
CSH Severity: Low
CVSS v4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-77756
CWE-ID: CWE-444
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause another user's request to fail.
The vulnerability exists due to improper handling of the Transfer-Encoding header in HTTP/1.0 request processing when processing an HTTP/1.0 request behind a reverse proxy. A remote attacker can send an HTTP/1.0 request with a Transfer-Encoding header to cause another user's request to fail.
The issue requires Tomcat to be located behind a reverse proxy.
Affected software
Apache Tomcat
How to mitigate CVE-2026-77756
Install security update from vendor's website.
Apache Tomcat - addressed in versions 9.0.122, 10.1.60, 11.0.26