# CVE-2026-12891: GStreamer gst-plugins-bad out-of-bounds read in H.266 parser

Source: https://junglewise.ai/threats/cve-2026-12891-gstreamer-gst-plugins-bad-out-of-bounds-read-in-h-266-parser  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-23. Updated: 2026-06-23  
License: CC BY 4.0 with a link back

CVE-2026-12891 · Severity: medium · CVSS 4.3 · Published 2026-06-23

GStreamer is a widely used multimedia framework for processing video and audio. A flaw in its H.266 video processing component allows a specially crafted video file to trigger an out-of-bounds memory read. This could allow an attacker to leak small amounts of sensitive information from the application's memory, potentially compromising user privacy or system security.

Technologies: [Gstreamer Gst-Plugins-Bad](https://junglewise.ai/threats/technologies/gst-plugins-bad), [Red Hat Enterprise Linux 10](https://junglewise.ai/threats/technologies/enterprise-linux-10), [Red Hat Enterprise Linux 8](https://junglewise.ai/threats/technologies/enterprise-linux-8), [Red Hat Enterprise Linux 9](https://junglewise.ai/threats/technologies/enterprise-linux-9). Vendors: [Gstreamer](https://junglewise.ai/threats/vendors/gstreamer), [Red Hat](https://junglewise.ai/threats/vendors/red-hat).

## Quick answers

**Is CVE-2026-12891 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-12891 being exploited in the wild.

**How severe is CVE-2026-12891?** Medium severity, with a CVSS score of 4.3, published 23 June 2026.

**Which products and versions are affected?** Gstreamer Gst-Plugins-Bad All versions containing H.266 parser; Red Hat Enterprise Linux 10 affected; Red Hat Enterprise Linux 8 affected; Red Hat Enterprise Linux 9 affected.

**Is there a fix for CVE-2026-12891?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-12891 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-12891?** Check whether you run Gstreamer Gst-Plugins-Bad, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8 or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An out-of-bounds read vulnerability exists in the GStreamer gst-plugins-bad package within the H.266/VVC VUI parameter parser. The root cause is a missing bounds check in the `gst_h266_parse_vui_parameters()` function in `gsth266parser.c`, where the `aspect_ratio_idc` field is used as an index into the `aspect_ratios[]` array. While the array contains only 17 entries, the 8-bit field allows values up to 255, leading to an 8-byte out-of-bounds read from the .data section. An attacker can exploit this by providing a malformed H.266 video stream, causing the leaked memory contents to be stored in video metadata (pixel-aspect-ratio), which can then be observed by downstream components or applications.

## Affected products

- GStreamer gst-plugins-bad All versions containing H.266 parser
- Red Hat Red Hat Enterprise Linux 8 affected
- Red Hat Red Hat Enterprise Linux 9 affected
- Red Hat Red Hat Enterprise Linux 10 affected

## Timeline

- 2026-06-22: disclosed: Reported by CoE-CNDS Lab to Red Hat Bugzilla
- 2026-06-23: advisory: NVD and Red Hat published advisory details

## References

- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)
- [https://access.redhat.com/security/cve/CVE-2026-12891](https://access.redhat.com/security/cve/CVE-2026-12891)
- [https://bugzilla.redhat.com/show_bug.cgi?id=2491318](https://bugzilla.redhat.com/show_bug.cgi?id=2491318)
- [https://gitlab.freedesktop.org/gstreamer/gstreamer/-/work_items/5109](https://gitlab.freedesktop.org/gstreamer/gstreamer/-/work_items/5109)

## Related threats

- [GStreamer gst-plugins-bad out-of-bounds read in MPEG/DVD parsing](https://junglewise.ai/threats/cve-2026-125706-a-flaw-was-found-in-gstreamer-s-gst-plugins-bad-mpeg-program)
- [GStreamer gst-plugins-bad MXF plugin buffer overflow in VANC handling](https://junglewise.ai/threats/cve-2026-125703-a-flaw-was-found-in-the-gstreamer-gst-plugins-bad-mxf-plugin)
- [GStreamer gst-plugins-bad H.265 uninitialized memory use](https://junglewise.ai/threats/cve-2026-121611-a-flaw-was-found-in-gstreamer-s-gst-plugins-bad-package-a-use-of)
- [GStreamer MXF demuxer out-of-bounds read](https://junglewise.ai/threats/cve-2026-121601-a-flaw-was-found-in-gstreamer-s-mxf-demuxer-plugin-gst-plugins)
- [GStreamer gst-plugins-bad JPEG 2000 decimator integer overflow and division by zero](https://junglewise.ai/threats/cve-2026-121259-a-flaw-was-found-in-the-gstreamer-jpeg-2000-decimator-in-gst)