GHSA-hrcp-8f3q-4w2c

### Impact
The vulnerability may allow a remote attacker to load and execute arbitrary code from a remote host only by manipulating the processed input stream. No user is affected, who followed the recommendation to setup XStream's security framework with a whitelist limited to the minimal required types.

### Patches
If you rely on XStream's default blacklist of the [Security Framework](https://x-stream.github.io/security.html#framework), you will have to use at least version 1.4.16.

### Workarounds
See [workarounds](https://x-stream.github.io/security.html#workaround) for the different versions covering all CVEs.

### References
See full information about the nature of the vulnerability and the steps to reproduce it in XStream's documentation for [CVE-2021-21351](https://x-stream.github.io/CVE-2021-21351.html).

### Credits
wh1t3p1g G5-RD6@IIE found and reported the issue to XStream and provided the required information to reproduce it.

### For more information
If you have any questions or comments about this advisory:
* Open an issue in [XStream](https://github.com/x-stream/xstream/issues)
* Contact us at [XStream Google Group](https://groups.google.com/group/xstream-user)