CVE-2022-24801 Overview
CVE-2022-24801 is an HTTP Request Smuggling vulnerability affecting Twisted, an event-based framework for internet applications supporting Python 3.6+. Prior to version 22.4.0rc1, the Twisted Web HTTP 1.1 server, located in the twisted.web.http module, parsed several HTTP request constructs more leniently than permitted by RFC 7230. This non-conformant parsing can lead to desynchronization when requests pass through multiple HTTP parsers, potentially enabling HTTP request smuggling attacks.
Critical Impact
Attackers can exploit this vulnerability to bypass security controls, poison web caches, hijack user sessions, or gain unauthorized access to backend systems by smuggling malicious HTTP requests through proxy chains.
Affected Products
- Twisted Twisted (versions prior to 22.4.0rc1)
- Debian Linux 9.0
- Fedora 35 and 36
- Oracle ZFS Storage Appliance Kit 8.8
Discovery Timeline
- 2022-04-04 - CVE-2022-24801 published to NVD
- 2024-11-25 - Last updated in NVD database
Technical Details for CVE-2022-24801
Vulnerability Analysis
This HTTP Request Smuggling vulnerability (CWE-444) stems from Twisted Web's HTTP 1.1 server parsing HTTP requests in a manner that does not strictly conform to RFC 7230 specifications. When Twisted is deployed behind a reverse proxy or load balancer, discrepancies in how each layer interprets HTTP request boundaries can be exploited by attackers.
The vulnerability specifically affects environments where HTTP requests traverse multiple parsers—for example, when Twisted serves as a backend behind nginx, Apache, or another HTTP proxy. Due to the lenient parsing behavior, an attacker can craft specially formatted requests that are interpreted differently by the front-end proxy and the Twisted backend, leading to request boundary desynchronization.
Root Cause
The root cause lies in the twisted.web.http module's HTTP 1.1 parser implementation, which accepts malformed or ambiguous HTTP request constructs that should be rejected according to RFC 7230. This lenient parsing creates interpretation discrepancies when requests pass through stricter or differently-implemented HTTP parsers upstream, enabling desync attacks.
Attack Vector
The attack is network-based and requires the attacker to send specially crafted HTTP requests to a server running Twisted Web behind a proxy or load balancer. The attack exploits differences in how the front-end and back-end servers parse HTTP request headers and body boundaries.
Exploitation typically involves manipulating headers such as Content-Length and Transfer-Encoding in ways that cause the front-end proxy and Twisted backend to disagree on where one request ends and another begins. This can allow an attacker to:
- Prepend malicious requests to legitimate user requests
- Bypass access controls and authentication mechanisms
- Poison web caches with malicious content
- Hijack other users' sessions
The Twisted Web client and HTTP 2.0 server are not affected, as they use different parsing implementations.
Detection Methods for CVE-2022-24801
Indicators of Compromise
- Unusual HTTP request patterns with conflicting Content-Length and Transfer-Encoding headers in server logs
- Evidence of cache poisoning or users receiving unexpected responses
- Authentication or authorization bypass events in application logs
- Anomalous request sequences where legitimate user requests appear to include unexpected payloads
Detection Strategies
- Monitor HTTP traffic for requests containing both Content-Length and Transfer-Encoding headers with conflicting values
- Implement web application firewall (WAF) rules to detect and block HTTP request smuggling patterns
- Audit Twisted installations to identify versions prior to 22.4.0rc1
- Review proxy and backend server logs for desynchronization indicators
Monitoring Recommendations
- Enable detailed HTTP request logging on both proxy and Twisted backend servers to identify parsing discrepancies
- Configure intrusion detection systems to alert on HTTP request smuggling attack signatures
- Implement application-level monitoring for unexpected authentication bypasses or session anomalies
- Regularly scan infrastructure for vulnerable Twisted versions using software composition analysis tools
How to Mitigate CVE-2022-24801
Immediate Actions Required
- Upgrade Twisted to version 22.4.0rc1 or later immediately
- Review and update all upstream proxies to ensure they are patched against HTTP request smuggling vulnerabilities
- Implement WAF rules to filter malformed HTTP requests at the network perimeter
- Audit all applications using Twisted Web to identify exposure
Patch Information
The vulnerability has been addressed in Twisted version 22.4.0rc1. The fix is available in the GitHub Commit. Organizations should upgrade to the patched version as soon as possible.
Additional security advisories and patches are available from:
Workarounds
- Ensure any vulnerabilities in upstream proxies have been addressed by upgrading them to current versions
- Filter malformed HTTP requests using upstream proxy configuration or WAF rules
- Configure proxies to normalize HTTP requests before forwarding to Twisted backends
- Consider implementing strict HTTP parsing at the proxy layer to reject ambiguous requests
# Upgrade Twisted using pip
pip install --upgrade twisted>=22.4.0
# Verify installed version
pip show twisted | grep Version
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
