{"id":"CVE-2019-18423","details":"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-\u003emax_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-\u003emax_mapped_gfn will be updated using the original frame. It would be possible to set p2m-\u003emax_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-\u003emax_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.","modified":"2026-03-15T22:31:06.492947Z","published":"2019-10-31T14:15:11.137Z","related":["MGASA-2020-0113","SUSE-SU-2019:2961-1","SUSE-SU-2019:3297-1","SUSE-SU-2019:3309-1","SUSE-SU-2019:3310-1"],"references":[{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2BQKX7M2RHCWDBKNPX4KEBI3MJIH6AYZ/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/I5WWPW4BSZDDW7VHU427XTVXV7ROOFFW/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IZYATWNUGHRBG6I3TC24YHP5Y3J7I6KH/"},{"type":"ADVISORY","url":"https://security.gentoo.org/glsa/202003-56"},{"type":"ADVISORY","url":"https://www.debian.org/security/2020/dsa-4602"},{"type":"ADVISORY","url":"https://seclists.org/bugtraq/2020/Jan/21"},{"type":"FIX","url":"http://www.openwall.com/lists/oss-security/2019/10/31/4"},{"type":"FIX","url":"http://xenbits.xen.org/xsa/advisory-301.html"}],"affected":[{"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2019-18423.json","unresolved_ranges":[{"events":[{"introduced":"4.8"},{"last_affected":"4.12.1"}]},{"events":[{"introduced":"0"},{"last_affected":"9.0"}]},{"events":[{"introduced":"0"},{"last_affected":"10.0"}]},{"events":[{"introduced":"0"},{"last_affected":"29"}]},{"events":[{"introduced":"0"},{"last_affected":"30"}]},{"events":[{"introduced":"0"},{"last_affected":"31"}]}]}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}