CVE-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 characters

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.

Exploitable with local access to the machine, without an account and if a user takes an action; an attacker can seriously compromise confidentiality, integrity or availability.

Attack vector

Local

Attack complexity

Low

Privileges required

None

Interaction

Required

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

High

Affected products and versions