CVE-2021-28701
That enforcement was missing, allowing guests to retain access to pages that were freed and perhaps re-used for other purposes.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.27%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
Another race in XENMAPSPACE_grant_table handling Guests are permitted access to certain Xen-owned pages of memory. The majority of such pages remain allocated / associated with a guest for its entire lifetime. Grant table v2 status pages, however, are de-allocated when a guest switches (back) from v2 to v1. Freeing such pages requires that the hypervisor enforce that no parallel request can result in the addition of a mapping of such a page to a guest. That enforcement was missing, allowing guests to retain access to pages that were freed and perhaps re-used for other purposes. Unfortunately, when XSA-379 was being prepared, this similar issue was not noticed.
- 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
- 0.27% probability · 19th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-362
- Affected
- xen/xen · debian/debian linux · fedoraproject/fedora
- Source
- security@xen.org
References
- http://www.openwall.com/lists/oss-security/2021/09/08/2Mailing List, Third Party Advisory
- http://xenbits.xen.org/xsa/advisory-384.htmlVendor Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3HEHUIUWSSMCQGQY3GWX4J2SZGYP5W2Z/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CEHZLIR5DFYYQBH55AERWHLO54OFU42C/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L4MI3MQAPGILCLXBGQWPZHGE3ALSO4ZU/
- https://security.gentoo.org/glsa/202208-23Third Party Advisory
- https://www.debian.org/security/2021/dsa-4977Third Party Advisory
- https://xenbits.xenproject.org/xsa/advisory-384.txtVendor Advisory
- http://www.openwall.com/lists/oss-security/2021/09/08/2Mailing List, Third Party Advisory
- http://xenbits.xen.org/xsa/advisory-384.htmlVendor Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3HEHUIUWSSMCQGQY3GWX4J2SZGYP5W2Z/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CEHZLIR5DFYYQBH55AERWHLO54OFU42C/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L4MI3MQAPGILCLXBGQWPZHGE3ALSO4ZU/
- https://security.gentoo.org/glsa/202208-23Third Party Advisory
- https://www.debian.org/security/2021/dsa-4977Third Party Advisory
- https://xenbits.xenproject.org/xsa/advisory-384.txtVendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.