# CVE-2026-56003: libXfont2 computeProps Property Buffer Heap Buffer Overflow

> Authenticated X clients can trigger a heap buffer overflow in libXfont2 to execute arbitrary code within the X server.

- **Severity:** High 8.5 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H`)
- **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 Jul 2026
- **Updated:** 9 Jul 2026
- **Also known as:** AZL-92084, BELL-CVE-2026-56003, CLSA-2026-1784797098, CLSA-2026-1784797435, CLSA-2026-1784798270, CLSA-2026-1787393547, DEBIAN-CVE-2026-56003, ECHO-232a-06a5-53fe, GHSA-3v92-8994-jg8p, UBUNTU-CVE-2026-56003

## What is CVE-2026-56003?

CVE-2026-56003 is a high-severity memory corruption vulnerability in X.Org libXfont2, published on 8 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A heap buffer overflow due to missing size checking in the property buffer when parsing PCF files in libXfont2 ComputeScaledProperties() before libXfont2 before 2.0.8 could be used by attackers using authenticated X clients to execute code within the X server.

Weakness: CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-56003?

It affects 1 product.


Products: X Libxfont.

## How do I fix CVE-2026-56003?

Upgrade to a fixed version.

## Is CVE-2026-56003 being exploited?

There is no known exploitation of CVE-2026-56003 in the wild and no public exploit code.

## Other vulnerabilities in X.Org libXfont2

- [CVE-2007-5199](https://insights.sbomify.com/CVE-2007-5199/): Memory corruption in n/a (critical 9.8)
- [CVE-2013-6462](https://insights.sbomify.com/CVE-2013-6462/): Memory corruption in n/a (critical 9.3)
- [CVE-2026-56001](https://insights.sbomify.com/CVE-2026-56001/): libXfont2 BitmapScaleBitmaps Integer Overflow Heap Buffer Overflow (high 8.5)
- [CVE-2026-56002](https://insights.sbomify.com/CVE-2026-56002/): libXfont2 PCF Font Parsing Heap Buffer Overflow (high 8.5)
- [CVE-2015-1802](https://insights.sbomify.com/CVE-2015-1802/): Memory corruption in n/a (high 8.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-56003 and fix it if it is affected.

What it is: CVE-2026-56003 is a high-severity memory corruption vulnerability in X.Org libXfont2, published on 8 Jul 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-2026-56003 in the wild and no public exploit code.

Affected product: X.Org libXfont2. 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-2026-56003/ (Markdown: https://insights.sbomify.com/CVE-2026-56003/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-56003
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-56003
- OSV: https://osv.dev/vulnerability/CVE-2026-56003

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-56003/
Summaries are generated and may contain mistakes; the official description above is the record.