### ImpactThe vulnerability may allow a remote attacker to request data from internal resources that are not publicly available 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.### PatchesIf 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.### WorkaroundsSee [workarounds](https://x-stream.github.io/security.html#workaround) for the different versions covering all CVEs.### ReferencesSee full information about the nature of the vulnerability and the steps to reproduce it in XStream's documentation for [CVE-2021-21349](https://x-stream.github.io/CVE-2021-21349.html).### CreditsThe vulnerability was discovered and reported by threedr3am.### For more informationIf 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)