Description

DOS vulnerability for Quoted Quality CSV headers

Impact

When Jetty handles a request containing request headers with a large number of “quality” (i.e. q) parameters (such as what are seen on the Accept, Accept-Encoding, and Accept-Language request headers), the server may enter a denial of service (DoS) state due to high CPU usage while sorting the list of values based on their quality values. A single request can easily consume minutes of CPU time before it is even dispatched to the application.

The only features within Jetty that can trigger this behavior are:

Default Error Handling - the Accept request header with the QuotedQualityCSV is used to determine what kind of content to send back to the client (html, text, json, xml, etc)

StatisticsServlet - uses the Accept request header with the QuotedQualityCSV to determine what kind of content to send back to the client (xml, json, text, html, etc)

HttpServletRequest.getLocale() - uses the Accept-Language request header with the QuotedQualityCSV to determine which “preferred” language is returned on this call.

HttpservletRequest.getLocales() - is similar to the above, but returns an ordered list of locales based on the quality values on the Accept-Language request header.

DefaultServlet - uses the Accept-Encoding request header with the QuotedQualityCSV to determine which kind of pre-compressed content should be sent back for static content (content that is not matched against a url-pattern in your web app)

Versions

QuotedQualityCSV was introduced to Jetty 9.3.9.v20160517 and the bug that introduced the vulnerability was in 9.4.6.v20170531.

Currently, known vulnerable versions include:

9.4.6.v20170531 thru to 9.4.36.v20210114

10.0.0

11.0.0

Workarounds

Quality ordered values are used infrequently by jetty so they can be avoided by:

Do not use the default error page/handler.

Do not deploy the StatisticsServlet exposed to the network

Do not call getLocale API

Do not enable precompressed static content in the DefaultServlet

Patches

All patches are available for download from the Eclipse Jetty website at https://www.eclipse.org/jetty/download.php

9.4.37.v20210219 and greater

10.0.1 and greater

11.0.1 and greater

Mitigation

Aliases

References