CVE-2021-26933

What it is

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.

At a glance

Exploitability

Can be exploited locally on the machine with a low-privilege account. High risk of data exposure.

Exploit odds

0.3% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-02-17 02:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:44 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.3% in the next 30 days (EPSS).
• Severity: 5.5 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-02-17 02:15 UTC

Last modified

2026-06-17 03:44 UTC

Exploit probability

0.3% · EPSS, next 30 days

Record status

Modified

Affected

• Xen ≤ 4.14.1
• Fedoraproject Fedora 32
• Fedoraproject Fedora 33
• Debian Linux 10.0

Attack profile CVSS 3.1 · 5.5

Attack vector

Local

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-26933.md and follow it. Check whether this project is affected by CVE-2021-26933. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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