Inconsistent interpretation of HTTP requests in Apache HTTP Server - CVE-2021-33193

Vulnerability identifier: #VU56474

CSH Severity: Medium

CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2021-33193

CWE-ID: CWE-444

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to preform HTTP/2 request smuggling attacks.

The vulnerability exists due to improper validation of HTTP/2 requests in mod_proxy in Apache HTTP Server. A remote attacker can send a specially crafted HTTP/2 request to the server and smuggle arbitrary HTTP headers.

Successful exploitation of vulnerability may allow an attacker to poison web server cache and perform phishing attacks.

Apache HTTP Server
Amazon Linux AMI
Gentoo Linux
SUSE CaaS Platform
SUSE Enterprise Storage
IBM i
Anolis OS
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
SUSE Linux Enterprise Server
SUSE Linux Enterprise Software Development Kit
Slackware Linux
SUSE Linux Enterprise Server for SAP
SUSE Linux Enterprise High Performance Computing
SUSE Linux Enterprise Module for Basesystem
SUSE Linux Enterprise Module for Server Applications
Ubuntu
Fedora
jbcs-httpd24-openssl-pkcs11 (Red Hat package)
jbcs-httpd24-openssl-chil (Red Hat package)
jbcs-httpd24-brotli (Red Hat package)
jbcs-httpd24-apr-util (Red Hat package)
jbcs-httpd24-apr (Red Hat package)
jbcs-httpd24-mod_http2 (Red Hat package)
jbcs-httpd24-nghttp2 (Red Hat package)
jbcs-httpd24-mod_md (Red Hat package)
httpd24-httpd (Red Hat package)
jbcs-httpd24-httpd (Red Hat package)
jbcs-httpd24-mod_security (Red Hat package)
jbcs-httpd24-jansson (Red Hat package)
jbcs-httpd24-curl (Red Hat package)
SUSE Linux Enterprise Module for Packagehub Subpackages
jbcs-httpd24-mod_proxy_cluster (Red Hat package)
mod_http2
mod_md
apache2-debuginfo
apache2-prefork-debuginfo
apache2-prefork
apache2-example-pages
apache2
apache2-devel
apache2-debugsource
apache2-utils
apache2-doc
apache2-utils-debuginfo
apache2-worker
apache2-worker-debuginfo
apache2-bin (Ubuntu package)
apache2 (Ubuntu package)
httpd-manual
httpd-filesystem
mod_ssl
mod_session
mod_proxy_html
mod_ldap
httpd-tools
httpd-devel
httpd
apache2-event-debuginfo
apache2-event
www-servers/apache
app-admin/apache-tools
EasyApache
Dell Secure Connect Gateway
IBM Aspera Orchestrator
IBM Power Hardware Management Console (HMC)
Tenable.sc
JBoss Core Services
IBM Aspera Faspex for Linux
IBM Aspera Faspex for Windows
Dell EMC Unity XT Operating Environment (OE)
Dell EMC Unity VSA Operating Environment (OE)
Dell EMC Unity Operating Environment (OE)
Maximo Application Suite - IoT Component
IBM Hardware Management Console

Install update from vendor's website.

Apache HTTP Server - update to 2.4.49
jbcs-httpd24-openssl-pkcs11 (Red Hat package) - addressed in versions 0.4.10-31.el7jbcs, 0.4.10-31.el8jbcs
jbcs-httpd24-openssl-chil (Red Hat package) - addressed in versions 1.0.0-16.el7jbcs, 1.0.0-16.el8jbcs
jbcs-httpd24-brotli (Red Hat package) - addressed in versions 1.0.9-2.el7jbcs, 1.0.9-2.el8jbcs
jbcs-httpd24-apr-util (Red Hat package) - addressed in versions 1.6.1-98.el7jbcs, 1.6.1-98.el8jbcs
jbcs-httpd24-apr (Red Hat package) - addressed in versions 1.7.0-6.el7jbcs, 1.7.0-6.el8jbcs
jbcs-httpd24-mod_http2 (Red Hat package) - addressed in versions 1.15.19-17.el7jbcs, 1.15.19-17.el8jbcs
jbcs-httpd24-nghttp2 (Red Hat package) - addressed in versions 1.43.0-10.el7jbcs, 1.43.0-10.el8jbcs
jbcs-httpd24-mod_md (Red Hat package) - addressed in versions 2.4.0-15.el7jbcs, 2.4.0-15.el8jbcs
httpd24-httpd (Red Hat package) - update to 2.4.34-23.el7.5
jbcs-httpd24-httpd (Red Hat package) - addressed in versions 2.4.51-28.el7jbcs, 2.4.51-28.el8jbcs
jbcs-httpd24-mod_security (Red Hat package) - addressed in versions 2.9.3-19.el7jbcs, 2.9.3-19.el8jbcs
jbcs-httpd24-jansson (Red Hat package) - addressed in versions 2.14-1.el7jbcs, 2.14-1.el8jbcs
EasyApache - update to 4 2021-9-22
Dell Secure Connect Gateway - update to 5.12.00.10
Tenable.sc - update to Patch 202110.1
jbcs-httpd24-curl (Red Hat package) - addressed in versions 7.83.1-6.el7jbcs, 7.83.1-6.el8jbcs
jbcs-httpd24-mod_proxy_cluster (Red Hat package) - addressed in versions 1.3.17-9.el7jbcs, 1.3.17-9.el8jbcs
mod_http2 - update to 1.15.7-5
mod_md - update to 2.0.8-8
apache2-debuginfo - addressed in versions 2.4.23-29.77.2, 2.4.33-3.55.1, 2.4.43-3.25.1
apache2-prefork-debuginfo - addressed in versions 2.4.23-29.77.2, 2.4.33-3.55.1, 2.4.43-3.25.1
apache2-prefork - addressed in versions 2.4.23-29.77.2, 2.4.33-3.55.1, 2.4.43-3.25.1
apache2-example-pages - update to 2.4.23-29.77.2
apache2 - addressed in versions 2.4.23-29.77.2, 2.4.33-3.55.1, 2.4.43-3.25.1
apache2-devel - addressed in versions 2.4.23-29.77.2, 2.4.33-3.55.1, 2.4.43-3.25.1
apache2-debugsource - addressed in versions 2.4.23-29.77.2, 2.4.33-3.55.1, 2.4.43-3.25.1
apache2-utils - addressed in versions 2.4.23-29.77.2, 2.4.33-3.55.1, 2.4.43-3.25.1
apache2-doc - addressed in versions 2.4.23-29.77.2, 2.4.33-3.55.1, 2.4.43-3.25.1
apache2-utils-debuginfo - addressed in versions 2.4.23-29.77.2, 2.4.33-3.55.1, 2.4.43-3.25.1
apache2-worker - addressed in versions 2.4.23-29.77.2, 2.4.33-3.55.1, 2.4.43-3.25.1
apache2-worker-debuginfo - addressed in versions 2.4.23-29.77.2, 2.4.33-3.55.1, 2.4.43-3.25.1
apache2-bin (Ubuntu package) - addressed in versions 2.4.29-1ubuntu4.17, 2.4.29-1ubuntu4.18, 2.4.41-4ubuntu3.5, 2.4.41-4ubuntu3.6, 2.4.46-4ubuntu1.2, 2.4.46-4ubuntu1.3, 2.4.182ubuntu3.17+esm3
apache2 (Ubuntu package) - addressed in versions 2.4.29-1ubuntu4.17, 2.4.29-1ubuntu4.18, 2.4.41-4ubuntu3.5, 2.4.41-4ubuntu3.6, 2.4.46-4ubuntu1.2, 2.4.46-4ubuntu1.3, 2.4.182ubuntu3.17+esm3
httpd-manual - update to 2.4.37-47.0.1
httpd-filesystem - update to 2.4.37-47.0.1
mod_ssl - update to 2.4.37-47.0.1
mod_session - update to 2.4.37-47.0.1
mod_proxy_html - update to 2.4.37-47.0.1
mod_ldap - update to 2.4.37-47.0.1
httpd-tools - update to 2.4.37-47.0.1
httpd-devel - update to 2.4.37-47.0.1
httpd - update to 2.4.37-47.0.1
apache2-event-debuginfo - update to 2.4.43-3.25.1
apache2-event - update to 2.4.43-3.25.1
httpd - addressed in versions 2.4.50-1.fc33, 2.4.50-1.fc34, 2.4.50-1.fc35
JBoss Core Services - update to 2.4.51
www-servers/apache - update to 2.4.54
app-admin/apache-tools - update to 2.4.54
IBM Aspera Orchestrator - update to 4.0.1.2b9681
IBM Aspera Faspex for Linux - update to 4.4.2
IBM Aspera Faspex for Windows - update to 4.4.2
Dell EMC Unity XT Operating Environment (OE) - update to 5.2.0.0.5.173
Dell EMC Unity VSA Operating Environment (OE) - update to 5.2.0.0.5.173
Dell EMC Unity Operating Environment (OE) - update to 5.2.0.0.5.173
Maximo Application Suite - IoT Component - addressed in versions 8.7.20, 8.8.16, 9.0.6
IBM Hardware Management Console - addressed in versions 9.2.950.0 SP3 ppc, 10.1.1020.0 SP1 ppc, 10.1.1020.0 SP1 x86
IBM Power Hardware Management Console (HMC) - addressed in versions 9.2.950.0 SP3, 10.1.1020.0 SP1

• https://portswigger.net/research/http2
• https://github.com/apache/httpd/commit/ecebcc035ccd8d0e2984fe41420d9e944f456b3c.patch
• https://downloads.apache.org/httpd/CHANGES_2.4

• HTTP request smuggling in Apache HTTP Server
• Slackware Linux update for httpd
• Multiple vulnerabilities in cPanel EasyApache
• Amazon Linux AMI update for httpd24
• Tenable.sc update for Apache HTTP Server
• Red Hat Enterprise Linux 8 update for the httpd:2.4 module
• SUSE update for apache2
• SUSE update for apache2
• SUSE update for apache2
• Ubuntu update for apache2
• Ubuntu update for apache2
• Ubuntu update for apache2
• Multiple vulnerabilities in DELL Secure Connect Gateway Security
• Gentoo update for Apache HTTPD
• Multiple vulnerabilities in IBM i
• Red Hat Software Collections update for httpd24-httpd
• Multiple vulnerabilities in IBM Aspera Faspex
• Multiple vulnerabilities in Red Hat JBoss Core Services
• IBM Power Hardware Management Console (HMC) update for Apache HTTP server
• Multiple vulnerabilities in IBM Hardware Management Console
• Inconsistent interpretation of HTTP requests in IBM Aspera Orchestrator
• Multiple vulnerabilities in Dell Unity, Dell UnityVSA, and Dell Unity XT
• Fedora 33 update for httpd
• Fedora 35 update for httpd
• Fedora 34 update for httpd
• Multiple vulnerabilities in IBM Maximo Application Suite - IoT Component
• Anolis OS update for httpd:2.4 module