CVE-2019-18423

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.

CVSS v3.0 8.8 HIGH
CVSS v2.0 8.5 HIGH

8.8^/10

CVSS v3.0 : HIGH

V3 Legend

Vector :

Exploitability : 2.8 / Impact : 5.9

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

8.5^/10

CVSS v2.0 : HIGH

V2 Legend

Vector : AV:N/AC:M/Au:S/C:C/I:C/A:C

Exploitability : 6.8 / Impact : 10.0

Access Vector NETWORK

Access Complexity MEDIUM

Authentication SINGLE

Confidentiality Impact COMPLETE

Integrity Impact COMPLETE

Availability Impact COMPLETE

References

Link	Resource
http://xenbits.xen.org/xsa/advisory-301.html	Patch Vendor Advisory
http://www.openwall.com/lists/oss-security/2019/10/31/4	Mailing List Patch Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/2BQKX7M2RHCWDBKNPX4KEBI3MJIH6AYZ/
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/I5WWPW4BSZDDW7VHU427XTVXV7ROOFFW/
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/IZYATWNUGHRBG6I3TC24YHP5Y3J7I6KH/
https://www.debian.org/security/2020/dsa-4602
https://seclists.org/bugtraq/2020/Jan/21
https://security.gentoo.org/glsa/202003-56

Configurations

Configuration 1 (hide)

cpe:2.3:o:xen:xen:*:*:*:*:*:*:arm:*

Information

Published : 2019-10-31 07:15

Updated : 2020-08-24 10:37

NVD link : CVE-2019-18423

Mitre link : CVE-2019-18423

JSON object : View

CWE

CWE-193

Off-by-one Error

Products Affected

xen

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8.8 /10