---
id: "CVE-2026-121406"
kind: "vulnerability"
aliases: ["CVE-2026-121406"]
title: "FreeRDP: malicious RDP server can crash client with zero-output payload"
severity: "medium"
cvss: 5.3
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["freerdp", "rdp", "remote-desktop", "runtime"]
not_affected_if: ["fixed-version", "trusted-servers-only"]
published_at: "2026-11-03T15:17:29+00:00"
first_seen_at: "2026-11-03T15:21:58+00:00"
updated_at: "2026-11-03T15:24:29+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-121406", "first_seen_at": "2026-11-03T15:21:58+00:00"}]
---

# FreeRDP: malicious RDP server can crash client with zero-output payload

FreeRDP's RDPGFX channel handler does not check for a null output from ZGFX decompression, so a zero-output payload triggers an assertion abort. A malicious RDP server can use this to terminate the connected FreeRDP client.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed FreeRDP version with `xfreerdp --version` or the package manager, and compare against the fixed version in the Fix section.
- Look for FreeRDP-based clients that connect to servers you do not control.

## Fix

- FreeRDP: move to `3.32.2` or later.

## Timeline

- 2026-11-03T15:21:58+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-121406

## Documents

- [advisory] Vendor advisory: github.com https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-2c9x-4gr7-hrwx
- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/freerdp-before-3.32.2-client-denial-of-service-via-zero-output-zgfx-payload

## From the sources

FreeRDP before 3.32.2 allows a client assertion abort because rdpgfx_on_data_received rejects only negative zgfx_decompress status and passes the resulting null output pointer to Stream_StaticConstInit. A malicious RDP server can send a zero-output ZGFX payload on the RDPGFX channel after session activation to terminate the client.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_