Vulnerability in Xen
CVE-2021-26933
An issue was discovered in Xen 4.9 through 4.14.x. On Arm, a guest is allowed to control whether memory accesses are bypassing the cache. This means that Xen needs to ensure that all writes (such as the ones during scrubbing) have reached the memory before handing over the page to a guest. Unfortunately, the operation to clean the cache is happening before checking if the page was scrubbed. Therefore there is no guarantee when all the writes will reach the memory.
EPSS: 0.003 (25.4th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N.
Affected products
- Xen
- Debian Debian_linux — versions 10.0
- Fedoraproject Fedora — versions 32, 33
- N/a — versions n/a
References
- cve@mitre.org (Patch, x_refsource_MISC, Vendor Advisory)
- cve@mitre.org (x_refsource_FEDORA, vendor-advisory)
- cve@mitre.org (x_refsource_FEDORA, vendor-advisory)
- cve@mitre.org (vendor-advisory, Third Party Advisory, x_refsource_DEBIAN)
Frequently asked questions
- What is CVE-2021-26933?
- CVE-2021-26933 is a medium-severity vulnerability in Xen. CVSS score: 5.5/10. Published 2021-02-17.
- How severe is CVE-2021-26933?
- Medium severity. CVSS v3 base score is 5.5 out of 10.