|Public release ||2016-11-22 12:00|
|Updated ||2016-11-22 12:00|
|Title ||guest 32-bit ELF symbol table load leaking host data|
Filesadvisory-194.txt (signed advisory file)
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Xen Security Advisory CVE-2016-9384 / XSA-194
guest 32-bit ELF symbol table load leaking host data
UPDATES IN VERSION 3
Along with their main kernel binary, unprivileged guests may arrange
to have their Xen environment load (kernel) symbol tables for their
use. The ELF image metadata created for this purpose has a few unused
bytes when the symbol table binary is in 32-bit ELF format. These
unused bytes were not properly cleared during symbol table loading.
A malicious unprivileged guest may be able to obtain sensitive
information from the host.
The information leak is small and not under the control of the guest,
so effectively exploiting this vulnerability is probably difficult.
Only Xen version 4.7 is affected. Xen versions 4.6 and earlier are not
The vulnerability is not exposed to x86 HVM guests, unless the host
toolstack has configured to load the guest with a non-default loader,
rather than hvmloader.
There is no known mitigation.
This issue was discovered by Roger Pau Monné of Citrix.
Applying the attached patch resolves this issue.
xsa194.patch xen-unstable, Xen 4.7.x
$ sha256sum xsa194*
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is then no longer applicable.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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Xenproject.org Security Team