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

> A malicious RealMedia file can trigger an out-of-bounds read in GStreamer, potentially leaking memory data or crashing the application.

- **Severity:** High 7.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 15 Jun 2026
- **Updated:** 5 Aug 2026
- **Also known as:** ALSA-2026:36673, DEBIAN-CVE-2026-53703, GHSA-hghw-p2mw-fvch, RLSA-2026:36673, UBUNTU-CVE-2026-53703

## What is CVE-2026-53703?

CVE-2026-53703 is a high-severity vulnerability in Red Hat Enterprise Linux 10, published on 15 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-53703?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `gstreamer1-plugins-ugly-free` | AlmaLinux:10 | All versions | 1.26.7-2.el10_2.1 |
| `gstreamer1-plugins-ugly-free` | Rocky Linux:10 | All versions | 0:1.26.7-2.el10_2.1 |

## How do I fix CVE-2026-53703?

Apply the vendor's patch.

## Is CVE-2026-53703 being exploited?

There is no known exploitation of CVE-2026-53703 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53703 and fix it if it is affected.

What it is: CVE-2026-53703 is a high-severity vulnerability in Red Hat Enterprise Linux 10, published on 15 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-53703 in the wild and no public exploit code.

Affected product: Red Hat Enterprise Linux 10. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-53703/ (Markdown: https://insights.sbomify.com/CVE-2026-53703/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53703
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53703
- OSV: https://osv.dev/vulnerability/CVE-2026-53703

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53703/
Summaries are generated and may contain mistakes; the official description above is the record.