CVE-2020-27223

DOS vulnerability for Quoted Quality CSV headers

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

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)

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2020-27223 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (9.4.37, 10.0.1, 11.0.1); upgrading removes the vulnerable code path.

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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

1. What is CVE-2020-27223? CVE-2020-27223 is a medium-severity uncontrolled resource consumption vulnerability in org.eclipse.jetty:jetty-server (maven), affecting versions >= 9.4.6, < 9.4.37. It is fixed in 9.4.37, 10.0.1, 11.0.1. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2020-27223? CVE-2020-27223 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of org.eclipse.jetty:jetty-server are affected by CVE-2020-27223? org.eclipse.jetty:jetty-server (maven) versions >= 9.4.6, < 9.4.37 is affected.
4. Is there a fix for CVE-2020-27223? Yes. CVE-2020-27223 is fixed in 9.4.37, 10.0.1, 11.0.1. Upgrade to this version or later.
5. Is CVE-2020-27223 exploitable, and should I be worried? Whether CVE-2020-27223 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2020-27223 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2020-27223?
   • Upgrade org.eclipse.jetty:jetty-server to 9.4.37 or later
   • Upgrade org.eclipse.jetty:jetty-server to 10.0.1 or later
   • Upgrade org.eclipse.jetty:jetty-server to 11.0.1 or later

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