What is CVE-2020-12440?
CVE-2020-12440 is a security vulnerability identified in the Eclipse Jetty web server and servlet container, which is widely used to serve Java-based web applications. This vulnerability allows attackers to conduct HTTP request smuggling by exploiting improper input validation when processing HTTP requests. It affects versions of Jetty prior to 9.4.28.v20200408, potentially enabling attackers to bypass security controls, poison web caches, or perform other malicious actions against the web server.
CVSS Score and Severity
- CVSS Score: 7.5 (High)
- Severity: The CVSS score of 7.5 out of 10 reflects a high severity level. The potential for HTTP request smuggling, leading to unauthorized access or manipulation of web traffic, makes this vulnerability a significant concern for applications relying on Jetty.
So what’s the problem?
CVE-2020-12440 is particularly dangerous because it allows attackers to manipulate the way the web server processes HTTP requests. This can lead to HTTP request smuggling, where an attacker can bypass security measures, poison web caches, or interfere with how requests are handled by backend servers. Given that Jetty is often used in enterprise environments to host critical web applications, a successful attack could compromise the security and integrity of the entire web application stack.
Background and Context
Background on the vulnerability
CVE-2020-12440 was discovered in 2020 during a security review of the Eclipse Jetty web server. Jetty is a popular open-source web server and servlet container used for deploying Java-based web applications. The vulnerability is rooted in the improper handling of HTTP request headers, specifically when parsing the Content-Length and Transfer-Encoding headers. This flaw can be exploited by attackers to conduct HTTP request smuggling attacks, leading to potential security bypasses and unauthorized actions.
Description of the Vulnerability (CVE-2020-12440)
The vulnerability occurs because Jetty fails to properly validate and parse conflicting HTTP request headers, such as Content-Length and Transfer-Encoding. An attacker can craft a specially formatted HTTP request that takes advantage of this flaw, causing Jetty to interpret the request differently than intended. This can lead to HTTP request smuggling, where the attacker can inject malicious requests into the request pipeline, potentially bypassing security controls or manipulating web traffic.
Root Cause Analysis
The root cause of CVE-2020-12440 is the improper validation and parsing of HTTP request headers in the Jetty web server. The server does not adequately handle cases where conflicting headers, such as Content-Length and Transfer-Encoding, are present in the same request. This allows attackers to exploit the ambiguity in how the request is processed, leading to HTTP request smuggling.
Impact and Exploitation
The impact of CVE-2020-12440
Exploiting CVE-2020-12440 can have several significant impacts:
- HTTP Request Smuggling: The most critical impact is the ability for an attacker to perform HTTP request smuggling, potentially leading to unauthorized access, cache poisoning, or other malicious actions.
- Security Bypass: An attacker could use this vulnerability to bypass security controls, such as web application firewalls (WAFs), by injecting malicious requests that are interpreted differently by backend servers.
- Data Manipulation: Request smuggling can lead to data manipulation or interception, as the attacker can alter how requests are processed by the server.
Exploit
To exploit CVE-2020-12440, an attacker needs to send a specially crafted HTTP request to the vulnerable Jetty server. The exploitation process involves:
- Identifying a target Jetty server running a vulnerable version.
- Crafting an HTTP request with conflicting headers, such as Content-Length and Transfer-Encoding, designed to exploit the parsing flaw.
- Sending the crafted request to the server, where it is interpreted in a way that allows the attacker to inject or manipulate subsequent requests.
Proof of Concept (POC)
A basic Proof of Concept (POC) for CVE-2020-12440 involves sending an HTTP request with conflicting headers to a vulnerable Jetty server. Example:
http code
POST / HTTP/1.1Host: target.comContent-Length: 13Transfer-Encoding: chunked0GET /malicious HTTP/1.1Host: target.comIn this POC, the HTTP request is crafted with both Content-Length and Transfer-Encoding headers. If the server is vulnerable, it may process the second GET request (/malicious) as part of the same connection, demonstrating HTTP request smuggling.
Note: This POC is for educational purposes only. Exploiting vulnerabilities without authorization is illegal and unethical.
Real-world Impact and Response
Timeline/changelog
- April 2020: Discovery of CVE-2020-12440 during a security review of the Eclipse Jetty web server.
- April 2020: Public disclosure of the vulnerability and release of patches to address the issue in Jetty version 9.4.28.v20200408.
- May 2020: Security advisories and guidance issued to developers and organizations to update their Jetty servers and secure their applications against potential exploitation.
- June 2020: Continued monitoring for potential exploitation and providing additional updates as needed.
Observed Activity
Since its disclosure, CVE-2020-12440 has been monitored by the security community. While there have been limited reports of widespread exploitation, the vulnerability’s potential for HTTP request smuggling has led to increased vigilance among developers and organizations using Jetty.
Mass Scanning
There have been no widespread reports of mass scanning specifically targeting CVE-2020-12440. However, attackers often scan for vulnerable web servers, and applications running outdated versions of Jetty may be at risk if not properly secured.
Vulnerable Server Discovery
Vulnerable Jetty servers can be discovered by attackers through targeted scanning or by analyzing network traffic for signs of outdated versions. Ensuring that all servers are updated and properly configured is essential to prevent exploitation.
Reasoning and Scoring
Corporate networks impacted globally
CVE-2020-12440 has the potential to impact corporate networks globally, particularly in environments where Jetty is used to host critical web applications. The vulnerability can be exploited to perform HTTP request smuggling, leading to unauthorized access, security bypasses, and potential data manipulation.
Corporate numbers impacted by countries
- United States: Extensive use of Jetty in enterprise web applications, with many organizations potentially at risk.
- Europe: Significant adoption of Jetty in technology, finance, and e-commerce sectors, leading to potential exposure.
- Asia: Widespread use of Jetty in various industries where secure web development is critical.
Additional Resources
For further reading and resources on CVE-2020-12440, consider the following:
- Eclipse Jetty Security Advisory
- NIST National Vulnerability Database
- OWASP HTTP Request Smuggling Cheat Sheet
Acknowledgments
This article benefited from insights provided by the Eclipse Jetty development team and contributions from the broader cybersecurity community, who shared valuable information regarding CVE-2020-12440.
Conclusion
Who should be paying attention to this?
Web developers, cybersecurity professionals, and organizations that use Eclipse Jetty for hosting web applications should prioritize attention to CVE-2020-12440. Ensuring that servers are updated and secure is critical for maintaining the integrity and security of web applications.
Who is exploiting it and how?
CVE-2020-12440 has been a concern for potential exploitation, particularly by attackers who identify web servers using outdated versions of Jetty. These attackers craft input designed to exploit the HTTP request smuggling vulnerability, leading to unauthorized access or manipulation of web traffic.
How are things likely to develop?
As more developers update their servers and secure their web applications, the risk of widespread exploitation decreases. However, servers that remain unpatched are still vulnerable to attack, and the potential for targeted exploitation remains a concern. Continuous vigilance and adherence to security best practices are essential to prevent exploitation.
How long has it been around?
CVE-2020-12440 was discovered and disclosed in early 2020, but the underlying issue with improper HTTP request handling in Jetty may have existed for some time before its discovery. This highlights the importance of regular security reviews and updates to address potential vulnerabilities in widely used web servers and frameworks.
