CVE-2021-26933 Race condition in n/a

What is CVE-2021-26933?

CVE-2021-26933 is a medium-severity vulnerability in Debian Debian Linux, published on 17 Feb 2021. It can only be exploited from the same machine or local network, with no action from the victim.

Official 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.

Which versions are affected by CVE-2021-26933?

It affects 3 products.

Products include Debian Debian Linux, Fedoraproject Fedora, Xen Xen.

How do I fix CVE-2021-26933?

Apply the vendor's patch.

Is CVE-2021-26933 being exploited?

There is no known exploitation of CVE-2021-26933 in the wild and no public exploit code.

Other vulnerabilities in Debian Debian Linux

• CVE-2015-3306 ProFTPD Improper Access Control Exploited Critical 10.0
• CVE-2025-49113 RoundCube Webmail Deserialization of Untrusted Data Exploited Critical 9.9
• CVE-2026-24061 GNU InetUtils Argument Injection Exploited Critical 9.8
• CVE-2025-39682 Linux Kernel Improper Check for Unusual or Exceptional Conditions Exploited Critical 9.8
• CVE-2024-9680 Mozilla Firefox Use-After-Free Exploited Critical 9.8

All Debian Debian Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as ALPINE-CVE-2021-26933, DEBIAN-CVE-2021-26933, GHSA-3c29-qfhr-mp78, UBUNTU-CVE-2021-26933.