CVE-2020-11739
An issue was discovered in Xen through 4.13.x, allowing guest OS users to cause a denial of service or possibly gain privileges because of missing memory barriers in read-write unlock paths.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.29%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
An issue was discovered in Xen through 4.13.x, allowing guest OS users to cause a denial of service or possibly gain privileges because of missing memory barriers in read-write unlock paths. The read-write unlock paths don't contain a memory barrier. On Arm, this means a processor is allowed to re-order the memory access with the preceding ones. In other words, the unlock may be seen by another processor before all the memory accesses within the "critical" section. As a consequence, it may be possible to have a writer executing a critical section at the same time as readers or another writer. In other words, many of the assumptions (e.g., a variable cannot be modified after a check) in the critical sections are not safe anymore. The read-write locks are used in hypercalls (such as grant-table ones), so a malicious guest could exploit the race. For instance, there is a small window where Xen can leak memory if XENMAPSPACE_grant_table is used concurrently. A malicious guest may be able to leak memory, or cause a hypervisor crash resulting in a Denial of Service (DoS). Information leak and privilege escalation cannot be excluded.
- CVSS 3.1
- 7.8 HIGHCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
- EPSS
- 0.29% probability · 21th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-362
- Affected
- xen/xen · fedoraproject/fedora · debian/debian linux · opensuse/leap
- Source
- cve@mitre.org
References
- http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00006.htmlMailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2020/04/14/2Mailing List, Patch, Third Party Advisory
- http://xenbits.xen.org/xsa/advisory-314.htmlPatch, Vendor Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5M2XRNCHOGGTJQBZQJ7DCV6ZNAKN3LE2/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NVTP4OYHCTRU3ONFJOFJQVNDFB25KLLG/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YMAW7D2MP6RE4BFI5BZWOBBWGY3VSOFN/
- https://security.gentoo.org/glsa/202005-08Third Party Advisory
- https://www.debian.org/security/2020/dsa-4723Third Party Advisory
- https://xenbits.xen.org/xsa/advisory-314.htmlPatch, Vendor Advisory
- http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00006.htmlMailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2020/04/14/2Mailing List, Patch, Third Party Advisory
- http://xenbits.xen.org/xsa/advisory-314.htmlPatch, Vendor Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5M2XRNCHOGGTJQBZQJ7DCV6ZNAKN3LE2/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NVTP4OYHCTRU3ONFJOFJQVNDFB25KLLG/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YMAW7D2MP6RE4BFI5BZWOBBWGY3VSOFN/
- https://security.gentoo.org/glsa/202005-08Third Party Advisory
- https://www.debian.org/security/2020/dsa-4723Third Party Advisory
- https://xenbits.xen.org/xsa/advisory-314.htmlPatch, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.