Medium · CVSS 6.1CVE-2026-100231

Gstreamer1-plugins-bad-free: gstreamer1-plugins-bad-free: heap out-of-bounds write in asfmux due to incorrect utf-16 size calculation for non-bmp charactersCVE-2026-100231

Answer in brief

CVE-2026-100231 records a Medium severity (CVSS 6.1) vulnerability in Gstreamer1-plugins-bad-free: gstreamer1-plugins-bad-free: heap out-of-bounds write in asfmux due to incorrect utf-16 size calculation for non-bmp characters. The current sources do not mark it as known exploited. The current feed maps Red Hat/gstreamer1-plugins-bad-free (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 14, 2026Updated Oct 14, 2026Source checked Oct 14, 2026First seen by HOL Oct 14, 2026Material review Oct 14, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 6.1
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Not reported

Why this deserves its current priority

CVSS is 6.1. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Red Hat/gstreamer1-plugins-bad-free (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Red Hat/gstreamer1-plugins-bad-freegeneric	*	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Red Hat/gstreamer1-plugins-bad-free.
Review the reported fix. Source-reported workaround: The asfmux plugin can be disabled at build time by passing `-Dgst-plugins-bad:asfmux=disabled` to meson when building GStreamer, or by removing/unloading the `libgstasfmux.so` shared library from the GStreamer plugin directory at runtime. Applications that do not require ASF muxing functionality are not affected. If ASF muxing is required, applications should sanitize metadata tags to remove non-BMP Unicode characters before passing them to the asfmux element.

Evidence timeline and material changes

Published upstream
Oct 14, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 14, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 14, 2026

Sources and claim methodology

Upstream source description

A flaw was found in the GStreamer multimedia framework's ASF muxer plugin (asfmux). When writing string metadata tags containing Unicode characters outside the Basic Multilingual Plane (such as emoji) to an ASF container, the plugin incorrectly calculates the buffer size needed for the UTF-16LE representation. The size calculation assumes each Unicode code point requires 2 bytes, but non-BMP characters require 4 bytes (surrogate pairs). This leads to a heap out-of-bounds write when the actual UTF-16LE conversion is written into the undersized buffer. An attacker could exploit this by providing media with crafted metadata tags to an application that transcodes or remuxes to ASF format while preserving metadata, potentially causing a denial of service or limited memory corruption.

Quoted source text, attributed separately from HOL analysis.