Vulnerability · Published Sep 8, 2021 · Assigned by XEN
CVE-2021-28701
High 7.8
In plain English
A high-severity security flaw in xen from Xen. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 19% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.20 | xen | 4.15.0-r3 | ALPINE-CVE-2021-28701 |
| Alpine:v3.21 | xen | 4.15.0-r3 | ALPINE-CVE-2021-28701 |
| Alpine:v3.22 | xen | 4.15.0-r3 | ALPINE-CVE-2021-28701 |
| Alpine:v3.23 | xen | 4.15.0-r3 | ALPINE-CVE-2021-28701 |
| Alpine:v3.24 | xen | 4.15.0-r3 | ALPINE-CVE-2021-28701 |
| Debian:12 | xen | 4.14.3-1 | DEBIAN-CVE-2021-28701 |
| Debian:13 | xen | 4.14.3-1 | DEBIAN-CVE-2021-28701 |
| Debian:14 | xen | 4.14.3-1 | DEBIAN-CVE-2021-28701 |
| Ubuntu:22.04:LTS | xen | no fix listed | UBUNTU-CVE-2021-28701 |
| Ubuntu:24.04:LTS | xen | no fix listed | UBUNTU-CVE-2021-28701 |
| Ubuntu:25.10 | xen | no fix listed | UBUNTU-CVE-2021-28701 |
| Ubuntu:26.04:LTS | xen | no fix listed | UBUNTU-CVE-2021-28701 |
| Ubuntu:26.10 | xen | no fix listed | UBUNTU-CVE-2021-28701 |
Affected products (as reported)
References
- https://xenbits.xenproject.org/xsa/advisory-384.txt x_refsource_MISC
- http://xenbits.xen.org/xsa/advisory-384.html x_refsource_CONFIRM
- [oss-security] 20210908 Xen Security Advisory 384 v3 (CVE-2021-28701) - Another race in XENMAPSPACE_grant_table handling mailing-list, x_refsource_MLIST
- FEDORA-2021-11577e5229 vendor-advisory, x_refsource_FEDORA
- FEDORA-2021-fed53cbc7d vendor-advisory, x_refsource_FEDORA
- DSA-4977 vendor-advisory, x_refsource_DEBIAN
- FEDORA-2021-5a0c7bc619 vendor-advisory, x_refsource_FEDORA
- GLSA-202208-23 vendor-advisory, x_refsource_GENTOO