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CVE-2026-41210

MEDIUMCVSS 6.5/10EPSS 0.31%

Last modified

CVE-2026-41210 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. 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. EPSS estimates a 0.31% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
6.5/10

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

EPSS Probability
0.31%

22.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
moonlight-streammoonlight-qt< 6.2.0

References

Timeline

Published
Last Modified
Status
Deferred

Frequently Asked Questions

What is CVE-2026-41210?
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.
How severe is CVE-2026-41210?
CVE-2026-41210 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 0.31% probability of exploitation in the next 30 days.
How do I fix CVE-2026-41210?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST