CVE-2025-6663 Overview
CVE-2025-6663 is a stack-based buffer overflow vulnerability in the GStreamer multimedia framework. The flaw resides in the parsing of H266 (Versatile Video Coding) Supplemental Enhancement Information (SEI) messages. Attackers can exploit this issue to execute arbitrary code in the context of the current process when a user opens or processes a malicious media file. The vulnerability was reported through Trend Micro's Zero Day Initiative as ZDI-CAN-27381.
Critical Impact
Successful exploitation allows arbitrary code execution within the process consuming the malicious H266 media stream, leading to full compromise of the user context.
Affected Products
- GStreamer multimedia framework (H266 codec parsing component)
- Applications and Linux distributions bundling vulnerable GStreamer builds
- Media players and pipelines relying on GStreamer for H266/VVC decoding
Discovery Timeline
- 2025-07-07 - CVE-2025-6663 published to the National Vulnerability Database (NVD)
- 2026-06-17 - Last updated in the NVD database
Technical Details for CVE-2025-6663
Vulnerability Analysis
The vulnerability exists in GStreamer's H266 SEI message parser. SEI messages carry optional metadata used during video decoding, including timing, color, and display information. The parser copies attacker-controlled data from an SEI payload into a fixed-length stack buffer without first validating that the supplied length fits within the destination. When the data exceeds the buffer size, the write overflows adjacent stack memory, including saved return addresses and frame pointers.
The weakness is classified under [CWE-121] Stack-based Buffer Overflow and [CWE-787] Out-of-bounds Write. Because GStreamer is embedded in many media players, browsers, and desktop environments, the parser is reachable through routine user activity such as previewing a video file or visiting a page that triggers media playback. Exploitation requires user interaction to load the crafted stream.
Root Cause
The root cause is the absence of bounds checking before copying user-supplied SEI payload data into a fixed-length stack-based buffer in the H266 parsing routine. The upstream fix is published in commit eedd01ac, which introduces proper length validation prior to the copy operation.
Attack Vector
The attack requires a local attack vector with user interaction. An attacker delivers a crafted H266 media file or stream to the victim through email attachments, web downloads, removable media, or media URLs handled by GStreamer-enabled applications. When the victim opens or previews the file, the malicious SEI message triggers the overflow and hijacks control flow within the decoder process. Code executes with the privileges of the user running the media application. Refer to the Zero Day Initiative Advisory ZDI-25-467 for additional technical detail.
Detection Methods for CVE-2025-6663
Indicators of Compromise
- Unexpected crashes or segmentation faults in gst-launch-1.0, totem, rhythmbox, or browser media processes when handling H266/VVC content
- Media player processes spawning shells, scripting interpreters, or network connections after opening a video file
- Writes to user directories or persistence locations originating from GStreamer plugin processes
Detection Strategies
- Inspect file metadata and MIME types for H266/VVC payloads delivered from untrusted sources
- Inventory installed GStreamer versions across endpoints and flag versions preceding the upstream fix commit eedd01ac
- Correlate media application crashes with subsequent process creation events to surface post-exploitation behavior
Monitoring Recommendations
- Enable core dump collection for GStreamer-based applications to capture overflow artifacts for forensic review
- Monitor child process creation from media decoder processes, which should rarely spawn shells or network clients
- Alert on outbound connections initiated by media playback processes immediately after file open events
How to Mitigate CVE-2025-6663
Immediate Actions Required
- Update GStreamer to a version that includes the upstream patch commit eedd01ac3dfeb60e36a44bb61a6d0418454e8416
- Apply distribution security updates for GStreamer packages such as gst-plugins-bad once vendors publish fixed builds
- Restrict opening of untrusted H266/VVC media files until patching is verified across the environment
Patch Information
The upstream fix is available in the GStreamer repository as commit eedd01ac. The patch adds length validation to the H266 SEI parsing path so oversized payloads are rejected before any copy into the stack buffer. Administrators should track downstream distribution advisories and deploy packaged updates as they become available.
Workarounds
- Disable or remove H266/VVC decoder plugins where the codec is not required for business operations
- Block delivery of H266/VVC media from external sources at email and web proxy gateways
- Run media-handling applications under reduced-privilege accounts or within sandboxes to limit exploitation impact
# Verify installed GStreamer version and locate H266 decoder elements
gst-inspect-1.0 --version
gst-inspect-1.0 | grep -i -E 'h266|vvc'
# Example: disable H266 elements by moving the plugin out of the search path
sudo mv /usr/lib/x86_64-linux-gnu/gstreamer-1.0/libgstvvc.so \
/usr/lib/x86_64-linux-gnu/gstreamer-1.0/libgstvvc.so.disabled
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
