---
id: "CVE-2026-121952"
kind: "vulnerability"
aliases: ["CVE-2026-121952"]
title: "FreeRDP proxy: out-of-bounds write lets a client corrupt server heap"
severity: "critical"
cvss: 9.8
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["freerdp", "proxy", "rdp", "runtime", "self-hosted"]
not_affected_if: ["client-only-use", "proxy-not-deployed"]
published_at: "2026-11-04T16:17:47+00:00"
first_seen_at: "2026-11-04T16:28:11+00:00"
updated_at: "2026-11-04T16:28:33+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-121952", "first_seen_at": "2026-11-04T16:28:11+00:00"}]
---

# FreeRDP proxy: out-of-bounds write lets a client corrupt server heap

FreeRDP's proxy component accepts a bitmap cache v2 capability value below five but then writes to fixed cell indices 0 through 4, causing out-of-bounds heap writes. A connecting client can corrupt heap memory, leak heap data to the backend, or crash the proxy.

_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 see whether it is below `3.32.2`.
- Confirm whether the FreeRDP proxy component is deployed in your environment.

## Fix

- FreeRDP: move to `3.32.2` or later

## Timeline

- 2026-11-04T16:28:11+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-121952

## Documents

- [advisory] Vendor advisory: github.com https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-xc85-4mqc-xgcx
- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/freerdp-before-3.32.2-proxy-out-of-bounds-write-via-bitmap-cache-v2-capability

## From the sources

FreeRDP before 3.32.2 has an out-of-bounds write in the proxy because rdp_read_bitmap_cache_v2_capability_set rejects only numCellCaches values above 5, yet the bitmap cache v2 cell array is later accessed at fixed indices 0 through 4. A client connecting to the proxy can declare fewer than five cell caches in its Confirm Active, causing heap corruption, heap data leakage to the backend, or a crash.

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