---
id: CVE-2026-77756
title: >-
  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 ano…
summary: >-
  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 ano…
severity: low
cvss: 3.7
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L'
cwe:
  - CWE-444
vendor: Apache Software Foundation
product: Apache Tomcat
affected:
  - apache_tomcat >= 11.0.0-M1 <= 11.0.25
  - apache_tomcat >= 10.1.0-M1 <= 10.1.59
  - apache_tomcat >= 9.0.47 <= 9.0.121
  - apache_tomcat >= 8.5.67 <= 8.5.100
published: '2026-09-23'
updated: '2026-09-23'
sourceUpdated: '2026-09-23T19:19:18.720'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-77756'
references:
  - url: 'https://lists.apache.org/thread/bl5b6rxqh3vb2k9bj2794vhor7o6xl3z'
    label: security@apache.org
  - url: 'http://www.openwall.com/lists/oss-security/2026/09/23/22'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-77756.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-77756'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2539351'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-77756'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-77756'
  - url: 'https://access.redhat.com/errata/RHSA-2026:68257'
  - url: 'https://access.redhat.com/errata/RHSA-2026:68258'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-23T13:18:16.430403Z'
ingestedAt: '2026-09-23T11:22:32.915Z'
epss: 0.00526
epssPercentile: 0.44377
patched:
  - hardened_images
scores:
  nvd: 3.7
  vendor: 5.3
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **RHSA-2026:68257** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:68257)
- **RHSA-2026:68258** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:68258)
- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat JBoss Web Server 5, … · updated 2026-09-29 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-77756.json)