CVE-2017-7559

In Undertow 2.x before 2.0.0.Alpha2, 1.4.x before 1.4.17.Final, and 1.3.x before 1.3.31.Final, it was found that the fix for CVE-2017-2666 was incomplete and invalid characters are still allowed in the query string and path parameters. This could be exploited, in conjunction with a proxy that also permitted the invalid characters but with a different interpretation, to inject data into the HTTP response. By manipulating the HTTP response the attacker could poison a web-cache, perform an XSS attack, or obtain sensitive information from requests other than their own.

CVE-2017-7559 has a CVSS score of 6.1 (Medium). The vector is network-reachable, no privileges required, and user interaction required. 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 (1.4.17.Final, 1.3.31.Final, 2.0.0.Alpha2); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2017-7559? CVE-2017-7559 is a medium-severity security vulnerability in io.undertow:undertow-core (maven), affecting versions >= 1.4.0, < 1.4.17.Final. It is fixed in 1.4.17.Final, 1.3.31.Final, 2.0.0.Alpha2.
2. How severe is CVE-2017-7559? CVE-2017-7559 has a CVSS score of 6.1 (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 io.undertow:undertow-core are affected by CVE-2017-7559? io.undertow:undertow-core (maven) versions >= 1.4.0, < 1.4.17.Final is affected.
4. Is there a fix for CVE-2017-7559? Yes. CVE-2017-7559 is fixed in 1.4.17.Final, 1.3.31.Final, 2.0.0.Alpha2. Upgrade to this version or later.
5. Is CVE-2017-7559 exploitable, and should I be worried? Whether CVE-2017-7559 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-2017-7559 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-2017-7559?
   • Upgrade io.undertow:undertow-core to 1.4.17.Final or later
   • Upgrade io.undertow:undertow-core to 1.3.31.Final or later
   • Upgrade io.undertow:undertow-core to 2.0.0.Alpha2 or later

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