# CVE-2026-40254: FreeRDP: contains_dotdot() off-by-one allows drive channel path traversal via terminal ..

> A rogue RDP server can read or write files outside the shared folder via path traversal if drive redirection is enabled.

- **Severity:** Medium 4.2 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N`)
- **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:** 24 Apr 2026
- **Updated:** 24 Apr 2026
- **Also known as:** DEBIAN-CVE-2026-40254, GHSA-3xpj-m4hx-8vmx, UBUNTU-CVE-2026-40254, openSUSE-SU-2026:10832-1

## What is CVE-2026-40254?

CVE-2026-40254 is a medium-severity path traversal vulnerability in Freerdp Freerdp, published on 24 Apr 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. Versions prior to 3.25.0 have an off-by-one in the path traversal filter in `channels/drive/client/drive_file.c`. The `contains_dotdot()` function catches `../` and `..\` mid-path but misses `..` when it's the last component with no trailing separator. A rogue RDP server can read, list, or write files one directory above the client's shared folder through RDPDR requests. This requires the victim to connect with drive redirection enabled. Version 3.25.0 patches the issue.

Weakness: CWE-193 (Off-by-one Error)

## Which versions are affected by CVE-2026-40254?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `freerdp` | openSUSE:Tumbleweed | All versions | 3.26.0-1.1 |

Products: Freerdp Freerdp.

## How do I fix CVE-2026-40254?

Upgrade to a fixed version.

## Is CVE-2026-40254 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40254 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-2026-40254 and fix it if it is affected.

What it is: CVE-2026-40254 is a medium-severity path traversal vulnerability in Freerdp Freerdp, published on 24 Apr 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-2026-40254 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-2026-40254/ (Markdown: https://insights.sbomify.com/CVE-2026-40254/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40254
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40254
- OSV: https://osv.dev/vulnerability/CVE-2026-40254

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40254/
Summaries are generated and may contain mistakes; the official description above is the record.