CVE-2026-41210

6.5Medium

Published 12 Oct 2026 · NVD status: Deferred · AI triage by gemini-3.8-flash

6.5Medium

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: Required
Impact: High impact on availability
Weakness: CWE-787

Impact

A malicious GameStream host can remotely crash the Moonlight client via heap corruption when a victim connects to it. Exploitation requires the user to initiate a streaming session to an untrusted host.

Root cause

The H.264 SPS fixup routine in ffmpeg.cpp uses the server-supplied seq_parameter_set_id as an array index without bounds checking, triggering an out-of-bounds write to the 32-entry sps_table.

Affected systems

Moonlight Qt version 6.1.0 and earlier

CVSS v3.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Fix & remediation

Upgrade Moonlight Qt to version 6.2.0 or later; avoid connecting to untrusted streaming hosts until updated.

AI-suggested. Run it in staging first and check it against the vendor advisory. Why?

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NVD description

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.

References

Source: nvd.nist.gov/vuln/detail/CVE-2026-41210