CVE-2019-18423

Current Description

An issue was discovered in Xen through 4.12.x allowing ARM guest OS users to cause a denial of service via a XENMEM_add_to_physmap hypercall. p2m->max_mapped_gfn is used by the functions p2m_resolve_translation_fault() and p2m_get_entry() to sanity check guest physical frame. The rest of the code in the two functions will assume that there is a valid root table and check that with BUG_ON(). The function p2m_get_root_pointer() will ignore the unused top bits of a guest physical frame. This means that the function p2m_set_entry() will alias the frame. However, p2m->max_mapped_gfn will be updated using the original frame. It would be possible to set p2m->max_mapped_gfn high enough to cover a frame that would lead p2m_get_root_pointer() to return NULL in p2m_get_entry() and p2m_resolve_translation_fault(). Additionally, the sanity check on p2m->max_mapped_gfn is off-by-one allowing "highest mapped + 1" to be considered valid. However, p2m_get_root_pointer() will return NULL. The problem could be triggered with a specially crafted hypercall XENMEM_add_to_physmap{, _batch} followed by an access to an address (via hypercall or direct access) that passes the sanity check but cause p2m_get_root_pointer() to return NULL. A malicious guest administrator may cause a hypervisor crash, resulting in a Denial of Service (DoS). Xen version 4.8 and newer are vulnerable. Only Arm systems are vulnerable. x86 systems are not affected.

Basic Data

PublishedOctober 31, 2019
Last ModifiedNovember 17, 2019
Assignercve@mitre.org
Data TypeCVE
Data FormatMITRE
Data Version4.0
Problem TypeCWE-20
CVE Data Version4.0

Base Metric V2

CVSS 2 - Version2.0
CVSS 2 - Vector StringAV:N/AC:M/Au:S/C:C/I:C/A:C
CVSS 2 - Access VectorNETWORK
CVSS 2 - Access ComplexityMEDIUM
CVSS 2 - AuthenticationSINGLE
CVSS 2 - Confidentiality ImpactCOMPLETE
CVSS 2 - Availability ImpactCOMPLETE
CVSS 2 - Base Score8.5
SeverityHIGH
Exploitability Score6.8
Impact Score10.0
Obtain All Privilegefalse
Obtain User Privilegefalse
Obtain Other Privilegefalse

Base Metric V3

No data provided.

Configurations

  • OR - Configuration 1
    Cpe VersionPartVendorProductVersionUpdateEditionLanguageSW EditionTarget SWTarget HWOtherVersion Start IncludingVersion End IncludingVersion Start ExcludingVersion End Excluding
    2.3OSXenXen******arm*4.84.12.1

Vulnerable Software List

VendorProductVersions
Xen Xen *

References

NameSourceURLTags
[oss-security] 20191031 Xen Security Advisory 301 v3 (CVE-2019-18423) - add-to-physmap can be abused to DoS Arm hostshttp://www.openwall.com/lists/oss-security/2019/10/31/4MLISTMailing List Patch Third Party Advisory
http://xenbits.xen.org/xsa/advisory-301.htmlhttp://xenbits.xen.org/xsa/advisory-301.htmlMISCPatch Vendor Advisory
FEDORA-2019-865bb16900https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/2BQKXFEDORA
FEDORA-2019-376ec5c107https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/I5WWPFEDORA
FEDORA-2019-cbb732f760https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/IZYATFEDORA
20200114 [SECURITY] [DSA 4602-1] xen security updatehttps://seclists.org/bugtraq/2020/Jan/21BUGTRAQ
GLSA-202003-56https://security.gentoo.org/glsa/202003-56GENTOO
DSA-4602https://www.debian.org/security/2020/dsa-4602DEBIAN