Vulnerabilities
Misconfiguration
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CVE Vulnerabilities

CVE-2020-11993

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

Published: Aug 07, 2020 | Modified: May 01, 2025
CVSS 3.x
7.5
HIGH
Source:
NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 2.x
4.3 MEDIUM
AV:N/AC:M/Au:N/C:N/I:N/A:P
RedHat/V2
RedHat/V3
7.5 MODERATE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Ubuntu
MEDIUM
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Additional information
NVDhttps://nvd.nist.gov/vuln/detail/CVE-2020-11993
CWEhttps://cwe.mitre.org/data/definitions/444.html

Apache HTTP Server versions 2.4.20 to 2.4.43 When trace/debug was enabled for the HTTP/2 module and on certain traffic edge patterns, logging statements were made on the wrong connection, causing concurrent use of memory pools. Configuring the LogLevel of mod_http2 above info will mitigate this vulnerability for unpatched servers.

Weakness

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.

Affected Software

NameVendorStart VersionEnd Version
Http_serverApache2.4.20 (including)2.4.44 (excluding)
JBoss Core Services on RHEL 6RedHatjbcs-httpd24-apr-0:1.6.3-104.jbcs.el6*
JBoss Core Services on RHEL 6RedHatjbcs-httpd24-apr-util-0:1.6.1-75.jbcs.el6*
JBoss Core Services on RHEL 6RedHatjbcs-httpd24-brotli-0:1.0.6-38.jbcs.el6*
JBoss Core Services on RHEL 6RedHatjbcs-httpd24-curl-0:7.64.1-44.jbcs.el6*
JBoss Core Services on RHEL 6RedHatjbcs-httpd24-httpd-0:2.4.37-64.jbcs.el6*
JBoss Core Services on RHEL 6RedHatjbcs-httpd24-jansson-0:2.11-53.jbcs.el6*
JBoss Core Services on RHEL 6RedHatjbcs-httpd24-mod_cluster-native-0:1.3.14-11.Final_redhat_2.jbcs.el6*
JBoss Core Services on RHEL 6RedHatjbcs-httpd24-mod_http2-0:1.15.7-11.jbcs.el6*
JBoss Core Services on RHEL 6RedHatjbcs-httpd24-mod_jk-0:1.2.48-10.redhat_1.jbcs.el6*
JBoss Core Services on RHEL 6RedHatjbcs-httpd24-mod_md-1:2.0.8-30.jbcs.el6*
JBoss Core Services on RHEL 6RedHatjbcs-httpd24-mod_security-0:2.9.2-57.GA.jbcs.el6*
JBoss Core Services on RHEL 6RedHatjbcs-httpd24-nghttp2-0:1.39.2-34.jbcs.el6*
JBoss Core Services on RHEL 6RedHatjbcs-httpd24-openssl-1:1.1.1c-32.jbcs.el6*
JBoss Core Services on RHEL 7RedHatjbcs-httpd24-apr-0:1.6.3-104.jbcs.el7*
JBoss Core Services on RHEL 7RedHatjbcs-httpd24-apr-util-0:1.6.1-75.jbcs.el7*
JBoss Core Services on RHEL 7RedHatjbcs-httpd24-brotli-0:1.0.6-38.jbcs.el7*
JBoss Core Services on RHEL 7RedHatjbcs-httpd24-curl-0:7.64.1-44.jbcs.el7*
JBoss Core Services on RHEL 7RedHatjbcs-httpd24-httpd-0:2.4.37-64.jbcs.el7*
JBoss Core Services on RHEL 7RedHatjbcs-httpd24-jansson-0:2.11-53.jbcs.el7*
JBoss Core Services on RHEL 7RedHatjbcs-httpd24-mod_cluster-native-0:1.3.14-11.Final_redhat_2.jbcs.el7*
JBoss Core Services on RHEL 7RedHatjbcs-httpd24-mod_http2-0:1.15.7-11.jbcs.el7*
JBoss Core Services on RHEL 7RedHatjbcs-httpd24-mod_jk-0:1.2.48-10.redhat_1.jbcs.el7*
JBoss Core Services on RHEL 7RedHatjbcs-httpd24-mod_md-1:2.0.8-30.jbcs.el7*
JBoss Core Services on RHEL 7RedHatjbcs-httpd24-mod_security-0:2.9.2-57.GA.jbcs.el7*
JBoss Core Services on RHEL 7RedHatjbcs-httpd24-nghttp2-0:1.39.2-34.jbcs.el7*
JBoss Core Services on RHEL 7RedHatjbcs-httpd24-openssl-1:1.1.1c-32.jbcs.el7*
JBoss Core Services on RHEL 7RedHatjbcs-httpd24-openssl-chil-0:1.0.0-1.jbcs.el7*
Red Hat Enterprise Linux 8RedHathttpd:2.4-8040020210127115317.9f9e2e7e*
Red Hat Software Collections for Red Hat Enterprise Linux 7RedHathttpd24-httpd-0:2.4.34-22.el7*
Red Hat Software Collections for Red Hat Enterprise Linux 7.6 EUSRedHathttpd24-httpd-0:2.4.34-22.el7*
Red Hat Software Collections for Red Hat Enterprise Linux 7.7 EUSRedHathttpd24-httpd-0:2.4.34-22.el7*
Text-Only JBCSRedHathttpd*
Apache2Ubuntubionic*
Apache2Ubuntudevel*
Apache2Ubuntuesm-infra/bionic*
Apache2Ubuntuesm-infra/focal*
Apache2Ubuntufocal*
Apache2Ubuntutrusty*
Apache2Ubuntuupstream*

Extended Description

HTTP requests or responses (“messages”) can be malformed or unexpected in ways that cause web servers or clients to interpret the messages in different ways than intermediary HTTP agents such as load balancers, reverse proxies, web caching proxies, application firewalls, etc. For example, an adversary may be able to add duplicate or different header fields that a client or server might interpret as one set of messages, whereas the intermediary might interpret the same sequence of bytes as a different set of messages. For example, discrepancies can arise in how to handle duplicate headers like two Transfer-encoding (TE) or two Content-length (CL), or the malicious HTTP message will have different headers for TE and CL. The inconsistent parsing and interpretation of messages can allow the adversary to “smuggle” a message to the client/server without the intermediary being aware of it. This weakness is usually the result of the usage of outdated or incompatible HTTP protocol versions in the HTTP agents.

Potential Mitigations

References

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