# CVE-2026-98900: xen/gntalloc: validate grant count before allocation


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 23 Oct 2026
- **Updated:** 26 Oct 2026
- **Also known as:** AZL-110656, BELL-CVE-2026-98900, DEBIAN-CVE-2026-98900, GHSA-mwrq-hx54-3h97, UBUNTU-CVE-2026-98900

## What is CVE-2026-98900?

CVE-2026-98900 is a vulnerability in Linux, published on 23 Oct 2026. 

### Official description

In the Linux kernel, the following vulnerability has been resolved:

xen/gntalloc: validate grant count before allocation

gntalloc_ioctl_alloc() allocates the grant-id array before checking
whether the requested count fits within the global grant limit. Counts
above that limit cannot succeed, so reject them before the
user-controlled allocation reaches kcalloc().

Use a subtraction-based check while holding gref_mutex so adding the
requested count cannot wrap. Also cast the count before advancing the
per-file index so the page-size multiplication is performed in 64-bit
arithmetic.

## Which versions are affected by CVE-2026-98900?


## How do I fix CVE-2026-98900?

Upgrade to a fixed version.

## Is CVE-2026-98900 being exploited?

There is no known exploitation of CVE-2026-98900 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98900 and fix it if it is affected.

What it is: CVE-2026-98900 is a vulnerability in Linux, published on 23 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-98900 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-98900/ (Markdown: https://insights.sbomify.com/CVE-2026-98900/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98900
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98900
- OSV: https://osv.dev/vulnerability/CVE-2026-98900

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98900/
Summaries are generated and may contain mistakes; the official description above is the record.