Bugzilla – Bug 1179510
VUL-0: CVE-2020-29486: xen: oxenstored: node ownership can be changed by unprivileged clients (XSA-352 v3)
Last modified: 2020-12-15 13:15:34 UTC
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Xen Security Advisory CVE-2020-29486 / XSA-352
oxenstored: node ownership can be changed by unprivileged clients
UPDATES IN VERSION 3
Nodes in xenstore have an ownership. In oxenstored, a owner could
give a node away. But node ownership has quota implications.
Any guest can run another guest out of quota, or create an unbounded
number of nodes owned by dom0, thus running xenstored out of memory
A malicious guest administrator can cause denial of service, against a
specific guest or against the whole host.
All systems using oxenstored are vulnerable. Building and using
oxenstored is the default in the upstream Xen distribution, if the
Ocaml compiler is available.
Systems using C xenstored are not vulnerable.
There are no mitigations.
Changing to use of C xenstored would avoid this vulnerability. However,
given the other vulnerabilities in both versions of xenstored being
reported at this time, changing xenstored implementation is not a
recommended approach to mitigation of individual issues.
This issue was discovered by Edwin Török of Citrix.
Applying the appropriate attached patch resolves this issue.
Note that patches for released versions are generally prepared to
apply to the stable branches, and may not apply cleanly to the most
recent release tarball. Downstreams are encouraged to update to the
tip of the stable branch before applying these patches.
xsa352.patch xen-unstable - 4.10
$ sha256sum xsa352*
DEPLOYMENT DURING EMBARGO
Deployment of the patches and/or mitigations described above (or
others which are substantially similar) is permitted during the
embargo, even on public-facing systems with untrusted guest users and
But: Distribution of updated software is prohibited (except to other
members of the predisclosure list).
Predisclosure list members who wish to deploy significantly different
patches and/or mitigations, please contact the Xen Project Security
(Note: this during-embargo deployment notice is retained in
post-embargo publicly released Xen Project advisories, even though it
is then no longer applicable. This is to enable the community to have
oversight of the Xen Project Security Team's decisionmaking.)
For more information about permissible uses of embargoed information,
consult the Xen Project community's agreed Security Policy:
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