CVE-2019-18421
published 2019-10-31CVE-2019-18421: An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to gain host OS privileges by leveraging race conditions in pagetable promotion…
PriorityP347high7.5CVSS 3.1
AVNACHPRLUINSUCHIHAH
EPSS
1.68%
74.5th percentile
An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to gain host OS privileges by leveraging race conditions in pagetable promotion and demotion operations. There are issues with restartable PV type change operations. To avoid using shadow pagetables for PV guests, Xen exposes the actual hardware pagetables to the guest. In order to prevent the guest from modifying these page tables directly, Xen keeps track of how pages are used using a type system; pages must be "promoted" before being used as a pagetable, and "demoted" before being used for any other type. Xen also allows for "recursive" promotions: i.e., an operating system promoting a page to an L4 pagetable may end up causing pages to be promoted to L3s, which may in turn cause pages to be promoted to L2s, and so on. These operations may take an arbitrarily large amount of time, and so must be re-startable. Unfortunately, making recursive pagetable promotion and demotion operations restartable is incredibly complicated, and the code contains several races which, if triggered, can cause Xen to drop or retain extra type counts, potentially allowing guests to get write access to in-use pagetables. A malicious PV guest administrator may be able to escalate their privilege to that of the host. All x86 systems with untrusted PV guests are vulnerable. HVM and PVH guests cannot exercise this vulnerability.
Affected
12 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | debian_linux | — | — |
| debian | debian_linux | — | — |
| debian | xen | < xen 4.11.3+24-g14b62ab3e5-1 (bookworm) | xen 4.11.3+24-g14b62ab3e5-1 (bookworm) |
| fedoraproject | fedora | — | — |
| fedoraproject | fedora | — | — |
| fedoraproject | fedora | — | — |
| opensuse | leap | — | — |
| xen | xen | <= 4.12.1 | — |
| xen | xen | >= 0 < 4.11.3+24-g14b62ab3e5-1 | 4.11.3+24-g14b62ab3e5-1 |
| xen | xen | >= 0 < 4.11.3+24-g14b62ab3e5-1 | 4.11.3+24-g14b62ab3e5-1 |
| xen | xen | >= 0 < 4.11.3+24-g14b62ab3e5-1 | 4.11.3+24-g14b62ab3e5-1 |
| xen | xen | >= 0 < 4.11.3+24-g14b62ab3e5-1 | 4.11.3+24-g14b62ab3e5-1 |
CVSS provenance
nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
nvdv2.07.1HIGHAV:N/AC:H/Au:S/C:C/I:C/A:C
osv7.5HIGH
vendor_debian7.5HIGH
vendor_redhat7.5HIGH
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Red Hat
xen: Further issues with restartable PV type change operations (XSA-310)
vendor_redhat·2019-12-11·CVSS 7.5
CVE-2019-19580 [HIGH] xen: Further issues with restartable PV type change operations (XSA-310)
xen: Further issues with restartable PV type change operations (XSA-310)
An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to gain host OS privileges by leveraging race conditions in pagetable promotion and demotion operations, because of an incomplete fix for CVE-2019-18421. XSA-299 addressed several critical issues in restartable PV type change operations. Despite extensive testing and auditing, some corner cases were missed. A malicious PV guest administrator may be able to escalate their privilege to that of the host. All security-supported versions of Xen are vulnerable. Only x86 systems are affected. Arm systems are not affected. Only x86 PV guests can leverage the vulnerability. x86 HVM and PVH guests cannot leverage the vulnerability. Note that these att
Red Hat
xen: a malicious PV guest administrator may be able to escalate their privilege to that of the host
vendor_redhat·2019-10-31·CVSS 7.5
CVE-2019-18421 [HIGH] CWE-268 xen: a malicious PV guest administrator may be able to escalate their privilege to that of the host
xen: a malicious PV guest administrator may be able to escalate their privilege to that of the host
An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to gain host OS privileges by leveraging race conditions in pagetable promotion and demotion operations. There are issues with restartable PV type change operations. To avoid using shadow pagetables for PV guests, Xen exposes the actual hardware pagetables to the guest. In order to prevent the guest from modifying these page tables directly, Xen keeps track of how pages are used using a type system; pages must be "promoted" before being used as a pagetable, and "demoted" before being used for any other type. Xen also allows for "recursive" promotions: i.e., an operating system promoting a page to an L4 pagetable ma
Debian
CVE-2019-19580: xen - An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to ...
vendor_debian·2019·CVSS 7.5
CVE-2019-19580 [HIGH] CVE-2019-19580: xen - An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to ...
An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to gain host OS privileges by leveraging race conditions in pagetable promotion and demotion operations, because of an incomplete fix for CVE-2019-18421. XSA-299 addressed several critical issues in restartable PV type change operations. Despite extensive testing and auditing, some corner cases were missed. A malicious PV guest administrator may be able to escalate their privilege to that of the host. All security-supported versions of Xen are vulnerable. Only x86 systems are affected. Arm systems are not affected. Only x86 PV guests can leverage the vulnerability. x86 HVM and PVH guests cannot leverage the vulnerability. Note that these attacks require very precise timing, which may be difficult to exploit in pra
Debian
CVE-2019-18421: xen - An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to ...
vendor_debian·2019·CVSS 7.5
CVE-2019-18421 [HIGH] CVE-2019-18421: xen - An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to ...
An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to gain host OS privileges by leveraging race conditions in pagetable promotion and demotion operations. There are issues with restartable PV type change operations. To avoid using shadow pagetables for PV guests, Xen exposes the actual hardware pagetables to the guest. In order to prevent the guest from modifying these page tables directly, Xen keeps track of how pages are used using a type system; pages must be "promoted" before being used as a pagetable, and "demoted" before being used for any other type. Xen also allows for "recursive" promotions: i.e., an operating system promoting a page to an L4 pagetable may end up causing pages to be promoted to L3s, which may in turn cause pages to be promoted to L2s, an
GHSA
GHSA-7g44-3rf3-p4xf: An issue was discovered in Xen through 4
ghsa_unreviewed·2022-05-24
CVE-2019-18421 [HIGH] CWE-362 GHSA-7g44-3rf3-p4xf: An issue was discovered in Xen through 4
An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to gain host OS privileges by leveraging race conditions in pagetable promotion and demotion operations. There are issues with restartable PV type change operations. To avoid using shadow pagetables for PV guests, Xen exposes the actual hardware pagetables to the guest. In order to prevent the guest from modifying these page tables directly, Xen keeps track of how pages are used using a type system; pages must be "promoted" before being used as a pagetable, and "demoted" before being used for any other type. Xen also allows for "recursive" promotions: i.e., an operating system promoting a page to an L4 pagetable may end up causing pages to be promoted to L3s, which may in turn cause pages to be promoted to L2s, an
GHSA
GHSA-5f2h-r2x9-9p3v: An issue was discovered in Xen through 4
ghsa_unreviewed·2022-05-24·CVSS 7.5
CVE-2019-19580 [HIGH] GHSA-5f2h-r2x9-9p3v: An issue was discovered in Xen through 4
An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to gain host OS privileges by leveraging race conditions in pagetable promotion and demotion operations, because of an incomplete fix for CVE-2019-18421. XSA-299 addressed several critical issues in restartable PV type change operations. Despite extensive testing and auditing, some corner cases were missed. A malicious PV guest administrator may be able to escalate their privilege to that of the host. All security-supported versions of Xen are vulnerable. Only x86 systems are affected. Arm systems are not affected. Only x86 PV guests can leverage the vulnerability. x86 HVM and PVH guests cannot leverage the vulnerability. Note that these attacks require very precise timing, which may be difficult to exploit in pra
OSV
CVE-2019-19580: An issue was discovered in Xen through 4
osv·2019-12-11·CVSS 7.5
CVE-2019-19580 [HIGH] CVE-2019-19580: An issue was discovered in Xen through 4
An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to gain host OS privileges by leveraging race conditions in pagetable promotion and demotion operations, because of an incomplete fix for CVE-2019-18421. XSA-299 addressed several critical issues in restartable PV type change operations. Despite extensive testing and auditing, some corner cases were missed. A malicious PV guest administrator may be able to escalate their privilege to that of the host. All security-supported versions of Xen are vulnerable. Only x86 systems are affected. Arm systems are not affected. Only x86 PV guests can leverage the vulnerability. x86 HVM and PVH guests cannot leverage the vulnerability. Note that these attacks require very precise timing, which may be difficult to exploit in pra
OSV
CVE-2019-18421: An issue was discovered in Xen through 4
osv·2019-10-31·CVSS 7.5
CVE-2019-18421 [HIGH] CVE-2019-18421: An issue was discovered in Xen through 4
An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to gain host OS privileges by leveraging race conditions in pagetable promotion and demotion operations. There are issues with restartable PV type change operations. To avoid using shadow pagetables for PV guests, Xen exposes the actual hardware pagetables to the guest. In order to prevent the guest from modifying these page tables directly, Xen keeps track of how pages are used using a type system; pages must be "promoted" before being used as a pagetable, and "demoted" before being used for any other type. Xen also allows for "recursive" promotions: i.e., an operating system promoting a page to an L4 pagetable may end up causing pages to be promoted to L3s, which may in turn cause pages to be promoted to L2s, an
No detection rules found.
No public exploits indexed.
Bugzilla
CVE-2019-18421 xen: a malicious PV guest administrator may be able to escalate their privilege to that of the host [fedora-all]
bugzilla·2019-11-01·CVSS 7.5
CVE-2019-18421 [HIGH] CVE-2019-18421 xen: a malicious PV guest administrator may be able to escalate their privilege to that of the host [fedora-all]
CVE-2019-18421 xen: a malicious PV guest administrator may be able to escalate their privilege to that of the host [fedora-all]
This is an automatically created tracking bug! It was created to ensure
that one or more security vulnerabilities are fixed in affected versions
of fedora-all.
For comments that are specific to the vulnerability please use bugs filed
against the "Security Response" product referenced in the "Blocks" field.
For more information see:
http://fedoraproject.org/wiki/Security/TrackingBugs
When submitting as an update, use the fedpkg template provided in the next
comment(s). This will include the bug IDs of this tracking bug as well as
the relevant top-level CVE bugs.
Please also mention the CVE IDs being fixed in the RPM changelog and the
fedpkg commit message.
NO
Bugzilla
CVE-2019-18421 xen: a malicious PV guest administrator may be able to escalate their privilege to that of the host
bugzilla·2019-10-24·CVSS 7.5
CVE-2019-18421 [HIGH] CVE-2019-18421 xen: a malicious PV guest administrator may be able to escalate their privilege to that of the host
CVE-2019-18421 xen: a malicious PV guest administrator may be able to escalate their privilege to that of the host
The code contains several races which, if triggered, can cause Xen to drop or retain extra type counts, potentially allowing guests to get write access to in-use pagetables.
Discussion:
Created xen tracking bugs for this issue:
Affects: fedora-all [bug 1767726]
http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00037.htmlhttp://www.openwall.com/lists/oss-security/2019/10/31/3http://xenbits.xen.org/xsa/advisory-299.htmlhttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2BQKX7M2RHCWDBKNPX4KEBI3MJIH6AYZ/https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/I5WWPW4BSZDDW7VHU427XTVXV7ROOFFW/https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IZYATWNUGHRBG6I3TC24YHP5Y3J7I6KH/https://seclists.org/bugtraq/2020/Jan/21https://security.gentoo.org/glsa/202003-56https://www.debian.org/security/2020/dsa-4602http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00037.htmlhttp://www.openwall.com/lists/oss-security/2019/10/31/3http://xenbits.xen.org/xsa/advisory-299.htmlhttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2BQKX7M2RHCWDBKNPX4KEBI3MJIH6AYZ/https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/I5WWPW4BSZDDW7VHU427XTVXV7ROOFFW/https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IZYATWNUGHRBG6I3TC24YHP5Y3J7I6KH/https://seclists.org/bugtraq/2020/Jan/21https://security.gentoo.org/glsa/202003-56https://www.debian.org/security/2020/dsa-4602
2019-10-31
Published