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AUSCERT External Security Bulletin Redistribution
New Xen bulletin: xen/arm: No memory limit for dom0less domUs
26 August 2021
AusCERT Security Bulletin Summary
Operating System: Xen
Impact/Access: Denial of Service -- Existing Account
CVE Names: CVE-2021-28700
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Xen Security Advisory CVE-2021-28700 / XSA-383
xen/arm: No memory limit for dom0less domUs
UPDATES IN VERSION 2
The dom0less feature allows an administrator to create multiple
unprivileged domains directly from Xen. Unfortunately, the
memory limit from them is not set. This allow a domain to allocate
memory beyond what an administrator originally configured.
Malicious dom0less guest could drive Xen out of memory and may
result to a Denial of Service (DoS) attack affecting the entire
Only Arm systems are vulnerable. Only domains created using the
dom0less feature are affected.
Only domains created using the dom0less feature can leverage the
All versions of Xen since 4.12 are vulnerable.
There is no known mitigation.
This issue was discovered by Julien Grall of Amazon.
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.
xsa383.patch xen-unstable - Xen 4.13.x
xsa383-4.12.patch Xen 4.12.x
$ sha256sum xsa383*
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is then no longer applicable.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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