Summary
Operation on a Resource after Expiration or Release in Jetty Server
In Eclipse Jetty, versions 9.4.27.v20200227 to 9.4.29.v20200521, in case of too large response headers, Jetty throws an exception to produce an HTTP 431 error. When this happens, the ByteBuffer containing the HTTP response headers is released back to the ByteBufferPool twice. Because of this double release, two threads can acquire the same ByteBuffer from the pool and while thread1 is about to use the ByteBuffer to write response1 data, thread2 fills the ByteBuffer with response2 data. Thread1 then proceeds to write the buffer that now contains response2 data. This results in client1, which issued request1 and expects responses, to see response2 which could contain sensitive data belonging to client2 (HTTP session ids, authentication credentials, etc.).
Impact
CVE-2019-17638 has a CVSS score of 9.4 (Critical). 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 (9.4.30.v20200611); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2019-17638? CVE-2019-17638 is a critical-severity security vulnerability in org.eclipse.jetty:jetty-server (maven), affecting versions >= 9.4.27, <= 9.4.30.v20200610. It is fixed in 9.4.30.v20200611.
- How severe is CVE-2019-17638? CVE-2019-17638 has a CVSS score of 9.4 (Critical). 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.
- Which versions of org.eclipse.jetty:jetty-server are affected by CVE-2019-17638? org.eclipse.jetty:jetty-server (maven) versions >= 9.4.27, <= 9.4.30.v20200610 is affected.
- Is there a fix for CVE-2019-17638? Yes. CVE-2019-17638 is fixed in 9.4.30.v20200611. Upgrade to this version or later.
- Is CVE-2019-17638 exploitable, and should I be worried? Whether CVE-2019-17638 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
- What actually determines whether CVE-2019-17638 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.
- How do I fix CVE-2019-17638? Upgrade
org.eclipse.jetty:jetty-serverto 9.4.30.v20200611 or later.