CVE-2021-28701

2021-09-0813:02:28

XEN

www.cve.org

7.9 High

AI Score

Confidence

High

0.0004 Low

EPSS

Percentile

14.2%

JSON

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.

CNA Affected

[
  {
    "product": "xen",
    "vendor": "Xen",
    "versions": [
      {
        "lessThan": "4.12",
        "status": "unknown",
        "version": "unspecified",
        "versionType": "custom"
      },
      {
        "lessThan": "unspecified",
        "status": "affected",
        "version": "4.15.x",
        "versionType": "custom"
      },
      {
        "lessThan": "unspecified",
        "status": "unaffected",
        "version": "next of xen-unstable",
        "versionType": "custom"
      }
    ]
  },
  {
    "product": "xen",
    "vendor": "Xen",
    "versions": [
      {
        "status": "affected",
        "version": "4.11.x"
      }
    ]
  },
  {
    "product": "xen",
    "vendor": "Xen",
    "versions": [
      {
        "lessThan": "4.12",
        "status": "unknown",
        "version": "unspecified",
        "versionType": "custom"
      },
      {
        "lessThan": "unspecified",
        "status": "affected",
        "version": "4.12.x",
        "versionType": "custom"
      },
      {
        "lessThan": "unspecified",
        "status": "unaffected",
        "version": "next of 4.14.x",
        "versionType": "custom"
      }
    ]
  }
]