---
id: CVE-2026-41210
title: 'Moonlight Qt is a GameStream client for Windows, macOS, Linux, and Steam Link'
summary: >-
  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
  selec…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H'
cwe:
  - CWE-787
published: '2026-10-12'
updated: '2026-10-12'
sourceUpdated: '2026-10-12T22:17:03.997'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-41210'
references:
  - url: >-
      https://github.com/moonlight-stream/moonlight-qt/commit/3e24a7a1a5369163482ce5a76d5232536e03c53f
    label: security-advisories@github.com
  - url: >-
      https://github.com/moonlight-stream/moonlight-qt/commit/b7adc70ea474f7448c6185081ad9fc87b0b47cf0
    label: security-advisories@github.com
  - url: 'https://github.com/moonlight-stream/moonlight-qt/releases/tag/v6.2.0'
    label: security-advisories@github.com
  - url: >-
      https://github.com/moonlight-stream/moonlight-qt/security/advisories/GHSA-5rvh-v25g-vrgv
    label: security-advisories@github.com
tags:
  - nvd
ingestedAt: '2026-10-12T23:07:25.635Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.