Inconsistent Interpretation of HTTP Requests
CWE-444
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.
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 This weakness is usually the result of the usage of outdated or incompatible HTTP protocol versions in the HTTP agents.
We track 174 vulnerabilities of this type. 99% are rated high or critical, and the average CVSS score is 8.4. 5 have been exploited in real attacks.
How this weakness is prevented
- Implementation: Use a web server that employs a strict HTTP parsing procedure, such as Apache.
- Implementation: Terminate the client session after each request.
Latest Inconsistent Interpretation of HTTP Requests vulnerabilities
- 9.1 Critical severity
Eclipse Jetty: Inconsistent Interpretation of HTTP Requests
In Eclipse Jetty, the HTTP/1.1 parser is vulnerable to request smuggling when chunk extensions are used, similar to the "funky chunks" techniques outlined here: * https://w4ke.info/2025/06/18/funky-chunks.html * https://w4ke.info/2025/10/29/funky-chunks-2.html
- 7.5 High severity
Apache Tomcat: Inconsistent Interpretation of HTTP Requests
Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in Apache Tomcat via invalid chunk extension. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.18, from 10.1.0-M1 through 10.1.52, from 9.0.0.M1 through
- 7.5 High severity
Tinyproxy: Inconsistent Interpretation of HTTP Requests
Tinyproxy through 1.11.3 is vulnerable to HTTP request parsing desynchronization due to a case-sensitive comparison of the Transfer-Encoding header in src/reqs.c. The is_chunked_transfer function uses strcmp to compare the header value against "chunked", even
- 7.5 High severity
Apache Traffic Server: Inconsistent Interpretation of HTTP Requests
Apache Traffic Server allows request smuggling if chunked messages are malformed. This issue affects Apache Traffic Server: from 9.0.0 through 9.2.12, from 10.0.0 through 10.1.1. Users are recommended to upgrade to version 9.2.13 or 10.1.2, which fix the issue
- 7.5 High severity
netty: Inconsistent Interpretation of HTTP Requests
Netty is an asynchronous, event-driven network application framework. In versions prior to 4.1.132.Final and 4.2.10.Final, Netty incorrectly parses quoted strings in HTTP/1.1 chunked transfer encoding extension values, enabling request smuggling attacks. Versi
- 9.1 Critical severity
Red Hat JBoss Enterprise Application Platform…: Inconsistent Interpretation of HTTP Requests
A flaw was found in Undertow. When Undertow receives an HTTP request where the first header line starts with one or more spaces, it incorrectly processes the request by stripping these leading spaces. This behavior, which violates HTTP standards, can be exploi
- 9.1 Critical severity
Red Hat JBoss Enterprise Application Platform…: Inconsistent Interpretation of HTTP Requests
A flaw was found in Undertow. This vulnerability allows a remote attacker to construct specially crafted requests where header names are parsed differently by Undertow compared to upstream proxies. This discrepancy in header interpretation can be exploited to
- 9.1 Critical severity
Red Hat JBoss Enterprise Application Platform…: Inconsistent Interpretation of HTTP Requests
A flaw was found in Undertow. A remote attacker can exploit this vulnerability by sending `\r\r\r` as a header block terminator. This can be used for request smuggling with certain proxy servers, such as older versions of Apache Traffic Server and Google Cloud
- 9.8 Critical severity
Firefox: Authentication Bypass Using an Alternate Path or Channel
Mitigation bypass in the Networking: HTTP component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
- 9.4 Critical severity
OTP: Inconsistent Interpretation of HTTP Requests
Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling') vulnerability in Erlang OTP (inets httpd module) allows HTTP Request Smuggling. This vulnerability is associated with program files lib/inets/src/http_server/httpd_request.erl and program
- 9.8 Critical severity
undici: Inconsistent Interpretation of HTTP Requests
Undici allows duplicate HTTP Content-Length headers when they are provided in an array with case-variant names (e.g., Content-Length and content-length). This produces malformed HTTP/1.1 requests with multiple conflicting Content-Length values on the wire. Who
- 9.1 Critical severity
TinyWeb: Integer Overflow or Wraparound
TinyWeb is a web server (HTTP, HTTPS) written in Delphi for Win32. Prior to version 2.03, an integer overflow vulnerability in the string-to-integer conversion routine (_Val) allows an unauthenticated remote attacker to bypass Content-Length restrictions and p
- 9.1 Critical severity
https://github.com/cloudflare/pingora: Inconsistent Interpretation of HTTP Requests
An HTTP Request Smuggling vulnerability (CWE-444) has been found in Pingora's parsing of HTTP/1.0 and Transfer-Encoding requests. The issue occurs due to improperly allowing HTTP/1.0 request bodies to be close-delimited and incorrect handling of multiple Trans
- 9.1 Critical severity
https://github.com/cloudflare/pingora: Inconsistent Interpretation of HTTP Requests
An HTTP request smuggling vulnerability (CWE-444) was found in Pingora's handling of HTTP/1.1 connection upgrades. The issue occurs when a Pingora proxy reads a request containing an Upgrade header, causing the proxy to pass through the rest of the bytes on th
- 9.8 Critical severity
h3: Inconsistent Interpretation of HTTP Requests
H3 is a minimal H(TTP) framework built for high performance and portability. Prior to 1.15.5, there is a critical HTTP Request Smuggling vulnerability. readRawBody is doing a strict case-sensitive check for the Transfer-Encoding header. It explicitly looks for
- 8.2 High severity
Red Hat Enterprise Linux 10: Inconsistent Interpretation of HTTP Requests
A flaw in libsoup’s HTTP header handling allows multiple Host: headers in a request and returns the last occurrence for server-side processing. Common front proxies often honor the first Host: header, so this mismatch can cause vhost confusion where a proxy ro
- 7.5 High severity
Platform Server: Inconsistent Interpretation of HTTP Requests
Outsystems Platform Server 11.18.1.37828 allows attackers to cause a denial of service via a crafted content-length value mismatching the body length. NOTE: the Supplier indicates that they are unable to reproduce this.
- 9.1 Critical severity
lighttpd: Inconsistent Interpretation of HTTP Requests
lighttpd1.4.80 incorrectly merged trailer fields into headers after http request parsing. This behavior can be exploited to conduct HTTP Header Smuggling attacks. Successful exploitation may allow an attacker to: * Bypass access control rules * Inject unsafe i
- 9.9 Critical severity
ASP.NET Core 2.3: Inconsistent Interpretation of HTTP Requests
Inconsistent interpretation of http requests ('http request/response smuggling') in ASP.NET Core allows an authorized attacker to bypass a security feature over a network.
- 7.5 High severity
Oracle E-Business Suite Server-Side Request Forgery (SSRF) Exploited
Vulnerability in the Oracle Configurator product of Oracle E-Business Suite (component: Runtime UI). Supported versions that are affected are 12.2.3-12.2.14. Easily exploitable vulnerability allows unauthenticated attacker with network access via HTTP to compr
- 7.5 High severity
http4s: Inconsistent Interpretation of HTTP Requests
Http4s is a Scala interface for HTTP services. In versions from 1.0.0-M1 to before 1.0.0-M45 and before 0.23.31, http4s is vulnerable to HTTP Request Smuggling due to improper handling of HTTP trailer section. This vulnerability could enable attackers to bypas
- 7.5 High severity
netty: Inconsistent Interpretation of HTTP Requests
Netty is an asynchronous event-driven network application framework for development of maintainable high performance protocol servers and clients. In versions 4.1.124.Final, and 4.2.0.Alpha3 through 4.2.4.Final, Netty incorrectly accepts standalone newline cha
- 9.1 Critical severity
eventlet: Inconsistent Interpretation of HTTP Requests
Eventlet is a concurrent networking library for Python. Prior to version 0.40.3, the Eventlet WSGI parser is vulnerable to HTTP Request Smuggling due to improper handling of HTTP trailer sections. This vulnerability could enable attackers to, bypass front-end
- 7.5 High severity
aiohttp: Inconsistent Interpretation of HTTP Requests
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.12.14, the Python parser is vulnerable to a request smuggling vulnerability due to not parsing trailer sections of an HTTP request. If a pure Python version of a
- 8.8 High severity
cpp-httplib: Inconsistent Interpretation of HTTP Requests
cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.20.1, cpp-httplib does not have a limit for a unique line, permitting an attacker to explore this to allocate memory arbitrarily. This vulnerability is fixed in 0.20.1
- 7.5 High severity
next.js: Inconsistent Interpretation of HTTP Requests
Next.js is a React framework for building full-stack web applications. From versions 15.0.4-canary.51 to before 15.1.8, a cache poisoning bug leading to a Denial of Service (DoS) condition was found in Next.js. This issue does not impact customers hosted on Ve
- 7.5 High severity
Classic Application Load Balancer: Inconsistent Interpretation of HTTP Requests
A request smuggling vulnerability existed in the Google Cloud Classic Application Load Balancer due to improper handling of chunked-encoded HTTP requests. This allowed attackers to craft requests that could be misinterpreted by backend servers. The issue was f
- 9.1 Critical severity
Cloud Waf: Inconsistent Interpretation of HTTP Requests
Radware Cloud Web Application Firewall (WAF) before 2025-05-07 allows remote attackers to bypass firewall filters by placing random data in the HTTP request body when using the HTTP GET method.
- 9.1 Critical severity
h11: Inconsistent Interpretation of HTTP Requests
h11 is a Python implementation of HTTP/1.1. Prior to version 0.16.0, a leniency in h11's parsing of line terminators in chunked-coding message bodies can lead to request smuggling vulnerabilities under certain conditions. This issue has been patched in version
- 7.5 High severity
Apache Traffic Server: Inconsistent Interpretation of HTTP Requests
Apache Traffic Server allows request smuggling if chunked messages are malformed. This issue affects Apache Traffic Server: from 9.2.0 through 9.2.9, from 10.0.0 through 10.0.4. Users are recommended to upgrade to version 9.2.10 or 10.0.5, which fixes the issu
- 7.5 High severity
react-router: Inconsistent Interpretation of HTTP Requests
React Router is a multi-strategy router for React bridging the gap from React 18 to React 19. There is a vulnerability in Remix/React Router that affects all Remix 2 and React Router 7 consumers using the Express adapter. Basically, this vulnerability allows a
- 7.5 High severity
benoitc/gunicorn: Inconsistent Interpretation of HTTP Requests
Gunicorn version 21.2.0 does not properly validate the value of the 'Transfer-Encoding' header as specified in the RFC standards, which leads to the default fallback method of 'Content-Length,' making it vulnerable to TE.CL request smuggling. This vulnerabilit
- 9.8 Critical severity
netease-youdao/qanything: Inconsistent Interpretation of HTTP Requests
HTTP Request Smuggling vulnerability in netease-youdao/qanything version 1.4.1 allows attackers to exploit inconsistencies in the interpretation of HTTP requests between a proxy and a server. This can lead to unauthorized access, bypassing security controls, s
- 10.0 Critical severity
libhv: Inconsistent Interpretation of HTTP Requests
Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in ithewei libhv allows HTTP Response Smuggling.This issue affects libhv: through 1.3.3.
- 7.1 High severity
OpenShift Service Mesh 2: Inconsistent Interpretation of HTTP Requests
A flaw was found in OpenShift Service Mesh 2.6.3 and 2.5.6. Rate-limiter avoidance, access-control bypass, CPU and memory exhaustion, and replay attacks may be possible due to improper HTTP header sanitization in Envoy.
- 7.4 High severity
Cryostat 4 on RHEL 9: Inconsistent Interpretation of HTTP Requests
A flaw was found in Quarkus-HTTP, which incorrectly parses cookies with certain value-delimiting characters in incoming requests. This issue could allow an attacker to construct a cookie value to exfiltrate HttpOnly cookie values or spoof arbitrary additional
- 7.5 High severity
aiohttp: Inconsistent Interpretation of HTTP Requests
aiohttp is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.10.11, the Python parser parses newlines in chunk extensions incorrectly which can lead to request smuggling vulnerabilities under certain conditions. If a pure
- 7.4 High severity
Migration Toolkit for Runtimes 1 on RHEL 8: Inconsistent Interpretation of HTTP Requests
A flaw was found in Undertow, which incorrectly parses cookies with certain value-delimiting characters in incoming requests. This issue could allow an attacker to construct a cookie value to exfiltrate HttpOnly cookie values or spoof arbitrary additional cook
- 7.5 High severity
libsoup: Inconsistent Interpretation of HTTP Requests
GNOME libsoup before 3.6.0 allows HTTP request smuggling in some configurations because '\0' characters at the end of header names are ignored, i.e., a "Transfer-Encoding\0: chunked" header is treated the same as a "Transfer-Encoding: chunked" header.
- 7.5 High severity
kmqtt: Inconsistent Interpretation of HTTP Requests
kmqtt v0.2.7 is vulnerable to Denial of Service (DoS) due to a Null Pointer Exception. A remote attacker can cause the broker to crash by sending a specially crafted MQTT CONNECT packet that triggers an unhandled null reference, leading to an immediate process