# CVE-2026-79603: Unconditionally do TLB flushing ahead of page scrubbing

> A race condition in Xen allows PV guests to modify scrubbed memory pages, potentially leading to data corruption or privilege escalation.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 Sep 2026
- **Updated:** 8 Sep 2026
- **Also known as:** ALPINE-CVE-2026-79603, DEBIAN-CVE-2026-79603, GHSA-pwv5-r8hr-fvgr, UBUNTU-CVE-2026-79603

## What is CVE-2026-79603?

CVE-2026-79603 is a medium-severity vulnerability in Xen, published on 8 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

x86 PV guests can free memory pages while still keeping a stale TLB entry
pointing to them.  A TLB flush is only issued by Xen (if needed) when the
page is re-used.  Since it's possible for the page to be scrubbed ahead of
the TLB flush, there's a window where a PV guest can modify an already
scrubbed page.

Weakness: CWE-664 (Improper Control of a Resource Through its Lifetime)

## Which versions are affected by CVE-2026-79603?


## How do I fix CVE-2026-79603?

Apply the vendor's patch.

## Is CVE-2026-79603 being exploited?

There is no known exploitation of CVE-2026-79603 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-79603 and fix it if it is affected.

What it is: CVE-2026-79603 is a medium-severity vulnerability in Xen, published on 8 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-79603 in the wild and no public exploit code.

Affected product: Xen. 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-2026-79603/ (Markdown: https://insights.sbomify.com/CVE-2026-79603/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-79603
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-79603
- OSV: https://osv.dev/vulnerability/CVE-2026-79603

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-79603/
Summaries are generated and may contain mistakes; the official description above is the record.