CVE-2026-63633
FreeRDP: Heap buffer overflow in Opus audio decode (`freerdp_dsp_decode_opus` resizes the wrong stream) — server→client
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.
INFO
Published Date :
Aug. 19, 2026, 6:17 p.m.
Last Modified :
Sept. 24, 2026, 3:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | CRITICAL | [email protected] | ||||
| CVSS 4.0 | HIGH | [email protected] |
Solution
- Update FreeRDP to version 3.28.0 or later.
- Ensure the client is not built with specific disabled configurations.
- Disable WAVE_FORMAT_OPUS if updating is not possible.
- Avoid connecting to untrusted RDP servers.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-63633.
| URL | Resource |
|---|---|
| https://github.com/FreeRDP/FreeRDP/commit/0ed1f95d36913581cf31124f94eb5843d4263eae | Patch |
| https://github.com/FreeRDP/FreeRDP/pull/12993 | Issue Tracking Patch |
| https://github.com/FreeRDP/FreeRDP/releases/tag/3.28.0 | Release Notes |
| https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-72j9-356v-88xq | Exploit Mitigation Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-63633 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-63633
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-63633 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-63633 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Sep. 24, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Added CPE Configuration OR *cpe:2.3:a:freerdp:freerdp:*:*:*:*:*:*:*:* versions up to (excluding) 3.28.0 Added Reference Type GitHub, Inc.: https://github.com/FreeRDP/FreeRDP/commit/0ed1f95d36913581cf31124f94eb5843d4263eae Types: Patch Added Reference Type GitHub, Inc.: https://github.com/FreeRDP/FreeRDP/pull/12993 Types: Issue Tracking, Patch Added Reference Type GitHub, Inc.: https://github.com/FreeRDP/FreeRDP/releases/tag/3.28.0 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-72j9-356v-88xq Types: Exploit, Mitigation, Vendor Advisory -
CVE Modified by [email protected]
Aug. 27, 2026
Action Type Old Value New Value Added Reference https://github.com/FreeRDP/FreeRDP/commit/0ed1f95d36913581cf31124f94eb5843d4263eae Added Reference https://github.com/FreeRDP/FreeRDP/pull/12993 Added Reference https://github.com/FreeRDP/FreeRDP/releases/tag/3.28.0 Added Reference https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-72j9-356v-88xq Removed Reference https://github.com/FreeRDP/FreeRDP/commit/0ed1f95d36913581cf31124f94eb5843d4263eae Removed Reference https://github.com/FreeRDP/FreeRDP/pull/12993 Removed Reference https://github.com/FreeRDP/FreeRDP/releases/tag/3.28.0 Removed Reference https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-72j9-356v-88xq -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 27, 2026
Action Type Old Value New Value Changed SSVC {'id': 'CVE-2026-63633', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'no'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-08-20T00:00:00+00:00'} {'id': 'CVE-2026-63633', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'no'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-08-21T03:55:50.964406Z'} -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 21, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-63633', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'no'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-08-20T00:00:00+00:00'} -
New CVE Received by [email protected]
Aug. 19, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'FreeRDP', 'product': 'FreeRDP', 'versions': [{'status': 'affected', 'version': '< 3.28.0'}]}] Added 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. Added CVSS V4.0 AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-122 Added Reference https://github.com/FreeRDP/FreeRDP/commit/0ed1f95d36913581cf31124f94eb5843d4263eae Added Reference https://github.com/FreeRDP/FreeRDP/pull/12993 Added Reference https://github.com/FreeRDP/FreeRDP/releases/tag/3.28.0 Added Reference https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-72j9-356v-88xq