Moonlight Stream Moonlight Qt up to 6.1.0 SPS Fixup ffmpeg.cpp seq_parameter_set_id out-of-bounds write

Summaryinfo

A vulnerability was found in Moonlight Stream Moonlight Qt up to 6.1.0. It has been declared as problematic. Affected is an unknown function of the file app/streaming/video/ffmpeg.cpp of the component SPS Fixup. Executing a manipulation of the argument seq_parameter_set_id can lead to out-of-bounds write. This vulnerability is tracked as CVE-2026-41210. The attack can be launched remotely. No exploit exists. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Moonlight Stream Moonlight Qt up to 6.1.0 and classified as problematic. This vulnerability affects some unknown processing of the file app/streaming/video/ffmpeg.cpp of the component SPS Fixup. The manipulation of the argument seq_parameter_set_id with an unknown input leads to a out-of-bounds write vulnerability. The CWE definition for the vulnerability is CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. As an impact it is known to affect availability. CVE summarizes:

Moonlight Qt is a GameStream client for Windows, macOS, Linux, and Steam Link. In version 6.1.0 and earlier, after a victim initiates a streaming session to a malicious host, the host can send a crafted H.264 SPS NAL when Moonlight selects a decoder path that does not advertise CAPABILITY_REFERENCE_FRAME_INVALIDATION_AVC. The SPS fixup path in app/streaming/video/ffmpeg.cpp parses the server-provided data with h264bitstream, where attacker-controlled seq_parameter_set_id is used to index the 32-entry sps_table without validation. A value of 32 or greater causes an out-of-bounds write and remote heap corruption in the Moonlight client. The demonstrated impact is a reliable client crash, while code execution is not established. This issue is fixed in version 6.2.0.

The advisory is available at github.com. This vulnerability was named CVE-2026-41210 since 04/18/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit.

Upgrading to version 6.2.0 eliminates this vulnerability.

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Productinfo

Vendor

• Moonlight Stream

Name

• Moonlight Qt

Version

• 6.0
• 6.1.0

CPE 2.3info

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CPE 2.2info

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