# CVE-2021-28706: xen: guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB of memory, it may be...

CVE-2021-28706 is fixed in xen on 1 platform, first by DEBIAN-CVE-2021-28706, released November 24, 2021. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2021-28706
- Priority: High
- CVSS: 8.6 (high)
- EPSS: 0.0223
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Nov 24, 2021

## Description

guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB of memory, it may be able to issue hypercalls to increase its memory allocation beyond the administrator established limit. This is a result of a calculation done with 32-bit precision, which may overflow. It would then only be the overflowed (and hence small) number which gets compared against the established upper bound.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | xen Debian 12.15 (bookworm) | 4.14.3+32-g9de3671772-1 | [DEBIAN-CVE-2021-28706](https://patchblox.com/security/data/fix/linux/debian-cve-2021-28706.md) | Nov 24, 2021 |
| Linux | xen Debian 13.5 (trixie) | 4.14.3+32-g9de3671772-1 | [DEBIAN-CVE-2021-28706](https://patchblox.com/security/data/fix/linux/debian-cve-2021-28706.md) | Nov 24, 2021 |
| Linux | xen Debian 14 | 4.14.3+32-g9de3671772-1 | [DEBIAN-CVE-2021-28706](https://patchblox.com/security/data/fix/linux/debian-cve-2021-28706.md) | Nov 24, 2021 |

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