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Debian LTS Advisory DLA-2769-1                [email protected]
https://www.debian.org/lts/security/                      Markus Koschany
September 29, 2021                            https://wiki.debian.org/LTS
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Package        : libxstream-java
Version        : 1.4.11.1-1+deb9u4
CVE ID         : CVE-2021-39139 CVE-2021-39140 CVE-2021-39141 CVE-2021-39144 
                 CVE-2021-39145 CVE-2021-39146 CVE-2021-39147 CVE-2021-39148 
                 CVE-2021-39149 CVE-2021-39150 CVE-2021-39151 CVE-2021-39152 
                 CVE-2021-39153 CVE-2021-39154

Multiple security vulnerabilities have been discovered in XStream, a Java
library to serialize objects to XML and back again. 

These vulnerabilities may allow a remote attacker to load and execute arbitrary
code from a remote host only by manipulating the processed input stream.

XStream itself sets up a whitelist by default now, i.e. it blocks all classes
except those types it has explicit converters for. It used to have a blacklist
by default, i.e. it tried to block all currently known critical classes of the
Java runtime. Main reason for the blacklist were compatibility, it allowed to
use newer versions of XStream as drop-in replacement. However, this approach
has failed. A growing list of security reports has proven, that a blacklist is
inherently unsafe, apart from the fact that types of 3rd libraries were not
even considered. A blacklist scenario should be avoided in general, because it
provides a false sense of security.

See also https://x-stream.github.io/security.html#framework

For Debian 9 stretch, these problems have been fixed in version
1.4.11.1-1+deb9u4.

We recommend that you upgrade your libxstream-java packages.

For the detailed security status of libxstream-java please refer to
its security tracker page at:
https://security-tracker.debian.org/tracker/libxstream-java

Further information about Debian LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at: https://wiki.debian.org/LTS