PT-2021-3349 · Xen+1 · Xen+1

Julien Grall · Published 2021-02-16 · Updated 2022-05-27 · CVE-2021-26933

Positive Technologies (AI Summary)

CVSS v3.1

5.5

Medium

Base vector

AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Name of the Vulnerable Software and Affected Versions Xen versions 4.9 through 4.14.x

Description An issue was discovered in Xen where a guest is allowed to control whether memory accesses are bypassing the cache on Arm systems. This means Xen needs to ensure all writes 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, resulting in no guarantee when all the writes will reach the memory.

Recommendations For Xen versions 4.9 through 4.14.x, as a temporary workaround, consider implementing additional checks to ensure that all writes have reached the memory before handing over the page to a guest, or restrict access to the cache cleaning operation until a proper fix is available. At the moment, there is no information about a newer version that contains a fix for this vulnerability.

Buffer Overflow

Weakness Enumeration

CWE-119

Related Identifiers

BDU:2021-03166

CVE-2021-26933

DSA-4888-1

Affected Products

Astra Linux

Xen

References · 27

• https://lists.fedoraproject.org/archives/list/[e-mail]/message/EOAJBVAVR6RSCUCHNXPVSNRPSFM7INMP · Vendor Advisory
• https://security-tracker.debian.org/tracker/CVE-2021-26933 · Vendor Advisory
• https://wiki.astralinux.ru/astra-linux-se17-bulletin-2021-1126SE17 · Vendor Advisory
• https://osv.dev/vulnerability/DEBIAN-CVE-2021-26933 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2021-26933 · Security Note
• https://cve.org/CVERecord?id=CVE-2021-26933 · Security Note
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EOAJBVAVR6RSCUCHNXPVSNRPSFM7INMP · Vendor Advisory
• https://bdu.fstec.ru/vul/2021-03166 · Security Note
• https://wiki.astralinux.ru/astra-linux-se47-bulletin-2022-0114SE47 · Vendor Advisory
• https://osv.dev/vulnerability/UBUNTU-CVE-2021-26933 · Vendor Advisory
• https://osv.dev/vulnerability/ALPINE-CVE-2021-26933 · Vendor Advisory
• http://xenbits.xen.org/xsa/advisory-364.html · Vendor Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4GELN5E6MDR5KQBJF5M5COUUED3YFZTD · Vendor Advisory
• https://debian.org/security/2021/dsa-4888 · Vendor Advisory
• https://ubuntu.com/security/CVE-2021-26933 · Vendor Advisory