CVSS2
Attack Vector
NETWORK
Attack Complexity
LOW
Authentication
NONE
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
PARTIAL
AV:N/AC:L/Au:N/C:N/I:N/A:P
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS
Percentile
87.1%
The vulnerability may allow a remote attacker to allocate 100% CPU time on the target system depending on CPU type or parallel execution of such a payload resulting in a denial of service only by manipulating the processed input stream.
XStream 1.4.19 monitors and accumulates the time it takes to add elements to collections and throws an exception if a set threshold is exceeded.
The attack uses the hash code implementation for collections and maps to force an exponential calculation time due to highly recursive structures with in the collection or map. Following types of the Java runtime are affected in Java versions available in December 2021:
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.
See full information about the nature of the vulnerability and the steps to reproduce it in XStream’s documentation for CVE-2021-43859.
The vulnerability was discovered and reported by r00t4dm at Cloud-Penetrating Arrow Lab.
If you have any questions or comments about this advisory:
Vendor | Product | Version | CPE |
---|---|---|---|
com.thoughtworks.xstream | xstream | * | cpe:2.3:a:com.thoughtworks.xstream:xstream:*:*:*:*:*:*:*:* |
www.openwall.com/lists/oss-security/2022/02/09/1
github.com/advisories/GHSA-rmr5-cpv2-vgjf
github.com/x-stream/xstream/commit/e8e88621ba1c85ac3b8620337dd672e0c0c3a846
github.com/x-stream/xstream/security/advisories/GHSA-rmr5-cpv2-vgjf
lists.debian.org/debian-lts-announce/2022/02/msg00018.html
lists.fedoraproject.org/archives/list/[email protected]/message/VACQYG356OHUTD5WQGAQ4L2TTFTAV3SJ/
lists.fedoraproject.org/archives/list/[email protected]/message/XODFRE2ZL64FICBJDOPWOLPTSSAI4U7X/
nvd.nist.gov/vuln/detail/CVE-2021-43859
www.oracle.com/security-alerts/cpuapr2022.html
www.oracle.com/security-alerts/cpujul2022.html
x-stream.github.io/CVE-2021-43859.html
CVSS2
Attack Vector
NETWORK
Attack Complexity
LOW
Authentication
NONE
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
PARTIAL
AV:N/AC:L/Au:N/C:N/I:N/A:P
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS
Percentile
87.1%