CVE-2026-63633
Description
A flaw was found in FreeRDP, a free implementation of the Remote Desktop Protocol. A malicious Remote Desktop Protocol (RDP) server can exploit a heap buffer overflow vulnerability during Opus audio decoding. This occurs when the server negotiates Opus audio with a vulnerable client, causing the client to write data beyond an allocated memory buffer. This can lead to client crashes, memory corruption, and potentially allow the malicious server to execute arbitrary code on the client system.
Statement
A heap buffer overflow vulnerability was found in FreeRDP's DSP audio codec module (libfreerdp/codec/dsp.c). When built with WITH_OPUS and without WITH_DSP_FFMPEG, freerdp_dsp_decode_opus fails to validate destination buffer capacity when handling WAVE_FORMAT_OPUS streams. A malicious RDP server can transmit an oversized Opus frame, causing libopus to write beyond the 4096-byte client buffer allocated by the rdpsnd channel. This leads to client heap corruption, application crashes, or potential remote code execution.
Mitigation
To mitigate this vulnerability, disable audio redirection on client connections by omitting audio parameters (such as `/sound` or `/audio`) in `xfreerdp` to bypass client-side DSP audio decoding.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.8 | N/A | N/A |
| Attack Vector | Network | N/A | N/A |
| Attack Complexity | Low | N/A | N/A |
| Privileges Required | None | N/A | N/A |
| User Interaction | Required | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | High | N/A | N/A |
| Integrity Impact | High | N/A | N/A |
| Availability Impact | High | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of the product's implicit security policy. This can often be used to subvert any other security service.
Availability
Technical Impact: Modify Memory; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU)
Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the product into an infinite loop.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
