# CVE-2026-23556: oxenstored keeps quota related use counts across domain destruction

> A flaw in Xen's oxenstored leaks quota usage counts, allowing a new domain to exhaust its quota prematurely and causing denial of service.

- **Severity:** Critical 9.4 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 9 Jul 2026
- **Updated:** 9 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-23556, GHSA-qcp2-2xf6-hw26, UBUNTU-CVE-2026-23556

## What is CVE-2026-23556?

CVE-2026-23556 is a critical denial of service vulnerability in oxenstored, published on 9 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

When oxenstored is tearing a domain down, the node data is cleaned up
but the usage counts are leaked.

When the domain ID is eventually reused, the new domain can create fewer
nodes before beeing deemed to be over quota.

Weakness: CWE-281 (Improper Preservation of Permissions)

## Which versions are affected by CVE-2026-23556?


## How do I fix CVE-2026-23556?

Apply the vendor's patch.

## Is CVE-2026-23556 being exploited?

There is no known exploitation of CVE-2026-23556 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-23556 and fix it if it is affected.

What it is: CVE-2026-23556 is a critical denial of service vulnerability in oxenstored, published on 9 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-23556 in the wild and no public exploit code.

Affected product: oxenstored. 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-2026-23556/ (Markdown: https://insights.sbomify.com/CVE-2026-23556/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23556
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23556
- OSV: https://osv.dev/vulnerability/CVE-2026-23556

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23556/
Summaries are generated and may contain mistakes; the official description above is the record.