CVE-2026-53701: GStreamer H.266/VVC Parser Out-of-Bounds Write Vulnerability

Technical summary

CVE-2026-53701 is an out-of-bounds write vulnerability (CWE-787) in GStreamer's gst_h266_parser_parse_picture_partition() function within gsth266parser.c. During multi-slice-in-tile processing of H.266/VVC picture partition information, the parser loop lacks bounds checking on the slice index variable. This permits writing past three fixed-size arrays in the GstH266PPS structure: slice_height_in_ctus, slice_top_left_ctu_x, and slice_top_left_ctu_y. While proof-of-concept testing demonstrated a 4-byte overflow, the parsing logic allows repeated iterations to write significantly larger amounts of data to adjacent memory. A crafted H.266/VVC bitstream embedded in media files can reliably trigger this condition.

Business impact

Organizations distributing or accepting H.266/VVC video content face denial-of-service risk if viewers use GStreamer-based applications. Video processing pipelines, transcoding services, and media servers relying on gst-plugins-bad are vulnerable. While memory corruption of this type could theoretically enable code execution under specific memory layouts, the CVSS rating reflects the primary impact as availability loss through application crashes. Teams managing video infrastructure or streaming services should treat this as a stability concern requiring prompt remediation.

Affected systems

GStreamer's gst-plugins-bad plugin module is affected, specifically versions containing the vulnerable gst_h266_parser_parse_picture_partition() function. Any application or service built on GStreamer for H.266/VVC video processing is at risk. This includes media players, transcoding software, live streaming infrastructure, and video analysis tools that enable H.266/VVC codec support. Verify your GStreamer version and whether H.266/VVC plugins are installed or enabled.

Exploitability

The vulnerability requires user interaction: a victim must open, play, or process a crafted H.266/VVC media file. No authentication is needed, and the attack vector is network-accessible (a file can be distributed via email, web, or streaming). The simplicity of crafting a malicious H.266/VVC bitstream to trigger unbounded loop iterations makes exploitation straightforward once a file reaches a target system. However, successful exploitation depends on memory layout and cannot be reliably weaponized for code execution in most scenarios, limiting the threat to application crashes.

Remediation

Update GStreamer and gst-plugins-bad to patched versions released by the GStreamer project. Consult the GStreamer security advisory and your distribution's package repositories for the specific version numbers applicable to your deployment. Organizations unable to patch immediately should disable H.266/VVC codec support if it is not essential, restrict processing of untrusted video files, or isolate video processing services to limit crash scope.

Patch guidance

Monitor GStreamer's official release channels and security advisories for patched versions. Most Linux distributions will provide updated gst-plugins-bad packages through their standard repositories. Verify patch application by confirming the fixed gst_h266_parser_parse_picture_partition() function now validates slice indices against array bounds before write operations. Testing with the original proof-of-concept file against the patched version should result in graceful error handling rather than a crash.

Detection guidance

Monitor for segmentation faults or application crashes in GStreamer-based processes when handling video content. Anomalous memory access patterns in gst_h266_parser_parse_picture_partition() detected through address sanitizers or kernel memory protection features may indicate exploitation attempts. File integrity monitoring on H.266/VVC samples can help identify suspicious bitstreams. Implement input validation at the application boundary to reject H.266/VVC files from untrusted sources until patching is complete.

Why prioritize this

Although unconfirmed for active exploitation in the wild (KEV not yet assigned), this vulnerability merits priority scheduling because it affects widely-deployed multimedia infrastructure, requires minimal attacker sophistication to trigger, and can immediately impact service availability. Organizations processing user-supplied video should prioritize patching. The CVSS 6.5 MEDIUM rating reflects denial-of-service impact; organizations with stricter stability requirements may elevate severity.

Risk score, explained

CVSS 3.1 score of 6.5 (MEDIUM severity) reflects: attack vector NETWORK (distributable via file), attack complexity LOW (simple bitstream crafting), no privileges required, user interaction required (user must process file), scope UNCHANGED, and impact as AVAILABILITY high (crash/DoS) with no confidentiality or integrity breach. The score appropriately captures a reliable but non-arbitrary crash condition. Memory corruption potential could theoretically warrant higher severity in specific architectural contexts, but standard assessment assumes non-exploitable crash behavior.

Frequently asked questions