{"id":"CVE-2021-26933","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-26933","generatedAt":"2026-10-27T23:30:01.986Z","title":"On Arm, a guest is allowed to control whether memory accesses are bypassing the cache.","description":"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.","published":"2021-02-17T02:15:13.000Z","lastModified":"2026-06-17T03:44:02.000Z","status":"Modified","sourceIdentifier":"cve@mitre.org","cvss":{"version":"3.1","score":5.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N"},"cwe":[],"affected":["xen/xen","fedoraproject/fedora","debian/debian linux"],"epss":{"score":0.00327,"percentile":0.25555,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.33%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"http://xenbits.xen.org/xsa/advisory-364.html","tags":["Patch","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4GELN5E6MDR5KQBJF5M5COUUED3YFZTD/","source":"cve@mitre.org"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EOAJBVAVR6RSCUCHNXPVSNRPSFM7INMP/","source":"cve@mitre.org"},{"url":"https://www.debian.org/security/2021/dsa-4888","tags":["Third Party Advisory"],"source":"cve@mitre.org"},{"url":"http://xenbits.xen.org/xsa/advisory-364.html","tags":["Patch","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4GELN5E6MDR5KQBJF5M5COUUED3YFZTD/","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EOAJBVAVR6RSCUCHNXPVSNRPSFM7INMP/","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.debian.org/security/2021/dsa-4888","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-26933","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}