# CVE-2026-63633: FreeRDP heap buffer overflow in Opus audio decoding

Source: https://junglewise.ai/threats/cve-2026-63633-freerdp-heap-buffer-overflow-in-opus-audio-decoding  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-19. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-63633 · Severity: critical · CVSS 9.8 · Published 2026-08-19

FreeRDP is a widely-used open-source client for connecting to remote desktops via the Remote Desktop Protocol. A malicious RDP server can trigger a heap buffer overflow in the audio codec when negotiating Opus audio format, allowing it to corrupt client memory, crash the application, or potentially execute arbitrary code on the victim's machine.

Technologies: [FreeRDP](https://junglewise.ai/threats/technologies/freerdp). Vendors: [FreeRDP](https://junglewise.ai/threats/vendors/freerdp).

## Quick answers

**Is CVE-2026-63633 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-63633 being exploited in the wild.

**How severe is CVE-2026-63633?** Critical severity, with a CVSS score of 9.8, published 19 August 2026.

**Which products and versions are affected?** FreeRDP prior to 3.28.0.

**Is there a fix for CVE-2026-63633?** A patch was published on 2026-07-02: Fix merged into master branch; released in version 3.28.0 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-63633 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-63633?** Check whether you run FreeRDP at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a heap buffer overflow in the freerdp_dsp_decode_opus function (libfreerdp/codec/dsp.c). The bug occurs because the code performs capacity checks on context->common.buffer, but the underlying opus_decode library writes decoded PCM audio into the caller-supplied output stream without respecting that buffer's bounds. When a client has Opus support enabled (WITH_OPUS) but FFmpeg DSP disabled (WITH_DSP_FFMPEG disabled), a malicious RDP server can negotiate WAVE_FORMAT_OPUS and send a large decoded audio frame (up to 5760 samples at 48 kHz) that exceeds the 4096-byte StreamPool allocation in rdpsnd_main.c, causing heap corruption. The attack requires network-level access to the RDP connection and no authentication bypass; the server-side negotiation is sufficient. This was fixed in version 3.28.0 by correcting buffer validation logic.

## Affected products

- FreeRDP FreeRDP prior to 3.28.0

## Timeline

- 2026-08-19: disclosed
- 2026-07-02: patched: Fix merged into master branch; released in version 3.28.0

## References

- [https://github.com/FreeRDP/FreeRDP/commit/0ed1f95d36913581cf31124f94eb5843d4263eae](https://github.com/FreeRDP/FreeRDP/commit/0ed1f95d36913581cf31124f94eb5843d4263eae)
- [https://github.com/FreeRDP/FreeRDP/pull/12993](https://github.com/FreeRDP/FreeRDP/pull/12993)

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