An issue was discovered in Xen 4.9 through 4.14.x.
Priority LOW 25Published · Updated
Key facts
- Attack vector
- Local
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- High · None · None
- Fix status
- No fix listed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA.
Summary
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.
Why it matters now
EPSS 0.00327 25th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | — | all versions | — | No fix listed | CNA |
- — Vendor— Affected all versions Fixed in — No fix listed CNA
CPE configurations NVD · 4
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:xen:xen:*:*:*:*:*:*:arm:* | 4.9.0 – 4.14.1 | Vulnerable | Xen |
| cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:* | 32 | Vulnerable | Fedoraproject |
| cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:* | 33 | Vulnerable | Fedoraproject |
| cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* | 10.0 | Vulnerable | Debian |
- cpe:2.3:o:xen:xen:*:*:*:*:*:*:arm:* Versions 4.9.0 – 4.14.1 Vulnerable ·Xen
- cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:* Versions 32 Vulnerable ·Fedoraproject
- cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:* Versions 33 Vulnerable ·Fedoraproject
- cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* Versions 10.0 Vulnerable ·Debian
Remediation
No fixed version listed by the sources yet.
Vendor assessments
Timeline
- 2026-10-02 Threatist record created from CVE-2021-26933
- 2026-10-03 Alias added: GHSA-3c29-qfhr-mp78
References
Sources
- CVE-2021-26933 · CVE Program
- CVE-2021-26933 · NVD
- FIRST EPSS
- GHSA-3c29-qfhr-mp78 · GitHub Advisory Database · CC BY 4.0
- CVE-2021-26933 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences