# CVE-2026-63409: Deskflow: Odd-length DSOP options vector causes out-of-bounds read in Deskflow client

> A malicious server can crash the Deskflow client by sending an odd-length options vector, causing an out-of-bounds read.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Aug 2026
- **Updated:** 18 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-63409, GHSA-gmvh-3c73-m5gg, UBUNTU-CVE-2026-63409

## What is CVE-2026-63409?

CVE-2026-63409 is a high-severity memory corruption vulnerability in deskflow, published on 17 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Deskflow is a keyboard and mouse sharing app. From 1.17.0 until continuous build 1.26.0.296, a malicious Deskflow server can send an odd-length DSOP vector to ServerProxy::setOptions() in src/lib/client/ServerProxy.cpp, causing the missing value after the final option key to be read beyond the vector during the PacketStreamFilter::filterEvent to ServerProxy::handleData() to ServerProxy::parseHandshakeMessage() call chain and crash the connected client. This issue is fixed in continuous build 1.26.0.296.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-63409?


## How do I fix CVE-2026-63409?

Upgrade to a fixed version.

## Is CVE-2026-63409 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-63409 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63409 and fix it if it is affected.

What it is: CVE-2026-63409 is a high-severity memory corruption vulnerability in deskflow, published on 17 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-63409 exists.

Affected product: deskflow. 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-2026-63409/ (Markdown: https://insights.sbomify.com/CVE-2026-63409/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63409
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63409
- OSV: https://osv.dev/vulnerability/CVE-2026-63409

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-63409/
Summaries are generated and may contain mistakes; the official description above is the record.