# CVE-2026-26955: FreeRDP has Out-of-bounds Write

> A malicious RDP server can trigger a heap buffer overflow in FreeRDP clients, leading to arbitrary code execution via corrupted function pointers.

- **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:** 25 Feb 2026
- **Updated:** 15 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-26955, GHSA-mr6w-ch7c-mqqj, UBUNTU-CVE-2026-26955

## What is CVE-2026-26955?

CVE-2026-26955 is a high-severity memory corruption vulnerability in Freerdp Freerdp, published on 25 Feb 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 version 3.23.0, a malicious RDP server can trigger a heap buffer overflow in FreeRDP clients using the GDI surface pipeline (e.g., `xfreerdp`) by sending an RDPGFX ClearCodec surface command with an out-of-bounds destination rectangle. The `gdi_SurfaceCommand_ClearCodec()` handler does not call `is_within_surface()` to validate the command rectangle against the destination surface dimensions, allowing attacker-controlled `cmd->left`/`cmd->top` (and subcodec rectangle offsets) to reach image copy routines that write into `surface->data` without bounds enforcement. The OOB write corrupts an adjacent `gdiGfxSurface` struct's `codecs*` pointer with attacker-controlled pixel data, and corruption of `codecs*` is sufficient to reach an indirect function pointer call (`NSC_CONTEXT.decode` at `nsc.c:500`) on a subsequent codec command — full instruction pointer (RIP) control demonstrated in exploitability harness. Users should upgrade to version 3.23.0 to receive a patch.

Weakness: CWE-805 (Buffer Access with Incorrect Length Value), CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-26955?

It affects 1 product.


Products: Freerdp Freerdp.

## How do I fix CVE-2026-26955?

Upgrade to a fixed version.

## Is CVE-2026-26955 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-26955 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-2026-26955 and fix it if it is affected.

What it is: CVE-2026-26955 is a high-severity memory corruption vulnerability in Freerdp Freerdp, published on 25 Feb 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-2026-26955 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-2026-26955/ (Markdown: https://insights.sbomify.com/CVE-2026-26955/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-26955
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-26955
- OSV: https://osv.dev/vulnerability/CVE-2026-26955

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-26955/
Summaries are generated and may contain mistakes; the official description above is the record.