CVE Vulnerabilities


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

Published: Jan 26, 2022 | Modified: Nov 07, 2023
CVSS 3.x
CVSS 2.x

In Varnish Cache before 6.6.2 and 7.x before 7.0.2, Varnish Cache 6.0 LTS before 6.0.10, and and Varnish Enterprise (Cache Plus) 4.1.x before 4.1.11r6 and 6.0.x before 6.0.9r4, request smuggling can occur for HTTP/1 connections.


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

Name Vendor Start Version End Version
Varnich_cache Varnish-software 1.0.0 (including) 6.6.2 (excluding)
Varnich_cache Varnish-software 4.1.1 (including) 4.1.11r6 (excluding)
Varnich_cache Varnish-software 4.1 (including) 4.1 (including)
Varnish_cache Varnish-software 6.0.0 (including) 6.0.10 (excluding)
Varnish_cache_plus Varnish-software 6.0.0 (including) 6.0.9r4 (excluding)
Varnish_cache Varnish_cache_project 7.0.0 (including) 7.0.2 (excluding)
Red Hat Enterprise Linux 8 RedHat varnish:6-8050020220201171716.c5368500 *
Red Hat Enterprise Linux 8.1 Update Services for SAP Solutions RedHat varnish:6-8010020220201182846.c27ad7f8 *
Red Hat Enterprise Linux 8.2 Extended Update Support RedHat varnish:6-8020020220201181211.4cda2c84 *
Red Hat Enterprise Linux 8.4 Extended Update Support RedHat varnish:6-8040020220201180030.522a0ee4 *
Red Hat Software Collections for Red Hat Enterprise Linux 7 RedHat rh-varnish6-varnish-0:6.0.8-2.el7.1 *
Varnish Ubuntu bionic *
Varnish Ubuntu esm-apps/bionic *
Varnish Ubuntu esm-apps/focal *
Varnish Ubuntu esm-apps/jammy *
Varnish Ubuntu focal *
Varnish Ubuntu impish *
Varnish Ubuntu jammy *
Varnish Ubuntu kinetic *
Varnish Ubuntu lunar *
Varnish Ubuntu trusty *
Varnish Ubuntu xenial *

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