# CVE-2026-44421: FreeRDP RDPGFX CacheToSurface heap-buffer-overflow via clamped-rectangle validation bypass

> A malicious RDP server can trigger a heap-buffer-overflow in FreeRDP clients with RDPGFX enabled, potentially leading to code execution or crashes.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 29 May 2026
- **Updated:** 27 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-44421, UBUNTU-CVE-2026-44421

## What is CVE-2026-44421?

CVE-2026-44421 is a high-severity memory corruption vulnerability in Freerdp Freerdp, published on 29 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.26.0, a malicious RDP server can trigger a heap-buffer-overflow write in the FreeRDP client by sending crafted RDPGFX PDUs. The bug is in gdi_CacheToSurface: it validates a destination rectangle that is clamped to UINT16_MAX, but then performs the copy using the original cacheEntry->width/height. This can cause a large out-of-bounds heap write and may lead to client crashes or code execution. This bug is reachable from a malicious RDP server, but only when the client has RDPGFX enabled. This vulnerability is fixed in 3.26.0.

Weakness: CWE-787 (Out-of-bounds Write), CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-44421?

It affects 1 product.


Products: Freerdp Freerdp.

## How do I fix CVE-2026-44421?

Upgrade to a fixed version.

## Is CVE-2026-44421 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44421 exists.

## Other vulnerabilities in Freerdp Freerdp

- [CVE-2021-37594](https://insights.sbomify.com/CVE-2021-37594/): Other in n/a (critical 9.8)
- [CVE-2021-37595](https://insights.sbomify.com/CVE-2021-37595/): Other in n/a (critical 9.8)
- [CVE-2026-67305](https://insights.sbomify.com/CVE-2026-67305/): FreeRDP Windows Client before 3.29.0 Heap Buffer Overflow via Cliprdr (critical 9.4)
- [CVE-2026-66402](https://insights.sbomify.com/CVE-2026-66402/): FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass (critical 9.3)
- [CVE-2026-67289](https://insights.sbomify.com/CVE-2026-67289/): FreeRDP before 3.29.0 HTTP Proxy Request Injection via Redirection (critical 9.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-44421 and fix it if it is affected.

What it is: CVE-2026-44421 is a high-severity memory corruption vulnerability in Freerdp Freerdp, published on 29 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44421 exists.

Affected product: Freerdp Freerdp. 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-2026-44421/ (Markdown: https://insights.sbomify.com/CVE-2026-44421/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-44421
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-44421
- OSV: https://osv.dev/vulnerability/CVE-2026-44421

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-44421/
Summaries are generated and may contain mistakes; the official description above is the record.