Summary
XStream can cause Denial of Service via stack overflow
Workarounds
The attack uses the hash code implementation for collections and maps to force recursive hash calculation causing a stack overflow. Following types of the Java runtime are affected:
- java.util.HashMap
- java.util.HashSet
- java.util.Hashtable
- java.util.LinkedHashMap
- java.util.LinkedHashSet
- Other third party collection implementations that use their element's hash code may also be affected
A simple solution is to catch the StackOverflowError in the client code calling XStream.
If your object graph does not use referenced elements at all, you may simply set the NO_REFERENCE mode:
XStream xstream = new XStream();
xstream.setMode(XStream.NO_REFERENCES);
If your object graph contains neither a Hashtable, HashMap nor a HashSet (or one of the linked variants of it) then you can use the security framework to deny the usage of these types:
XStream xstream = new XStream();
xstream.denyTypes(new Class[]{
java.util.HashMap.class, java.util.HashSet.class, java.util.Hashtable.class, java.util.LinkedHashMap.class, java.util.LinkedHashSet.class
});
Unfortunately these types are very common. If you only use HashMap or HashSet and your XML refers these only as default map or set, you may additionally change the default implementation of java.util.Map and java.util.Set at unmarshalling time::
xstream.addDefaultImplementation(java.util.TreeMap.class, java.util.Map.class);
xstream.addDefaultImplementation(java.util.TreeSet.class, java.util.Set.class);
However, this implies that your application does not care about the implementation of the map and all elements are comparable.
References
See full information about the nature of the vulnerability and the steps to reproduce it in XStream's documentation for CVE-2022-41966.
For more information
If you have any questions or comments about this advisory:
- Open an issue in XStream
- Contact us at XStream Google Group
Impact
The vulnerability may allow a remote attacker to terminate the application with a stack overflow error resulting in a denial of service only by manipulating the processed input stream.
Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect. Typical impact: arbitrary code execution or logic abuse.
CVE-2022-41966 has a CVSS score of 8.2 (High). 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 (1.4.20); 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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XStream 1.4.20 handles the stack overflow and raises an InputManipulationException instead.
Frequently Asked Questions
- What is CVE-2022-41966? CVE-2022-41966 is a high-severity insecure deserialization vulnerability in com.thoughtworks.xstream:xstream (maven), affecting versions < 1.4.20. It is fixed in 1.4.20. Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect.
- How severe is CVE-2022-41966? CVE-2022-41966 has a CVSS score of 8.2 (High). 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 com.thoughtworks.xstream:xstream are affected by CVE-2022-41966? com.thoughtworks.xstream:xstream (maven) versions < 1.4.20 is affected.
- Is there a fix for CVE-2022-41966? Yes. CVE-2022-41966 is fixed in 1.4.20. Upgrade to this version or later.
- Is CVE-2022-41966 exploitable, and should I be worried? Whether CVE-2022-41966 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-2022-41966 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-2022-41966? Upgrade
com.thoughtworks.xstream:xstreamto 1.4.20 or later.