CVE-2023-40167: Jetty accepts "+" prefixed value in Content-Length
Impact
Jetty accepts the '+' character proceeding the content-length value in a HTTP/1 header field. This is more permissive than allowed by the RFC and other servers routinely reject such requests with 400 responses. There is no known exploit scenario, but it is conceivable that request smuggling could result if jetty is used in combination with a server that does not close the connection after sending such a 400 response.
Workarounds
There is no workaround as there is no known exploit scenario.
Original Report
RFC 9110 Secion 8.6 defined the value of Content-Length header should be a string of 0-9 digits. However we found that Jetty accepts "+" prefixed Content-Length, which could lead to potential HTTP request smuggling.
Payload:
POST / HTTP/1.1 Host: a.com Content-Length: +16 Connection: close 0123456789abcdef
When sending this payload to Jetty, it can successfully parse and identify the length.
When sending this payload to NGINX, Apache HTTPd or other HTTP servers/parsers, they will return 400 bad request.
This behavior can lead to HTTP request smuggling and can be leveraged to bypass WAF or IDS.
Other sources
Jetty is a Java based web server and servlet engine. Prior to versions 9.4.52, 10.0.16, 11.0.16, and 12.0.1, Jetty accepts the + character proceeding the content-length value in a HTTP/1 header field. This is more permissive than allowed by the RFC and other servers routinely reject such requests with 400 responses. There is no known exploit scenario, but it is conceivable that request smuggling could result if jetty is used in combination with a server that does not close the connection after sending such a 400 response. Versions 9.4.52, 10.0.16, 11.0.16, and 12.0.1 contain a patch for this issue. There is no workaround as there is no known exploit scenario.
Affected Software
Event History
Frequently Asked Questions
What is CVE-2023-40167?
CVE-2023-40167 is a vulnerability in Jetty, a Java-based web server and servlet engine, that allows the '+' character preceding the content-length value in an HTTP/1 header field, which is more permissive than allowed by the RFC and can lead to potential security issues.
What is the impact of CVE-2023-40167?
The impact of CVE-2023-40167 is that Jetty accepts requests with the '+' character before the content-length value, which is not compliant with the RFC and may be rejected by other servers. Although there is no known exploit scenario, it could potentially be used for request smuggling attacks.
What is the severity of CVE-2023-40167?
CVE-2023-40167 has a severity rating of 5.3, which is considered medium.
How can I fix CVE-2023-40167?
To fix CVE-2023-40167, it is recommended to upgrade to versions 9.4.52, 10.0.16, 11.0.16, or 12.0.1 of Jetty to ensure compliance with the RFC and mitigate potential security risks.
Where can I find more information about CVE-2023-40167?
More information about CVE-2023-40167 can be found in the following references: [GitHub Advisory](https://github.com/eclipse/jetty.project/security/advisories/GHSA-hmr7-m48g-48f6), [RFC 9110](https://www.rfc-editor.org/rfc/rfc9110#section-8.6), and [NVD](https://nvd.nist.gov/vuln/detail/CVE-2023-40167).