CVE-2026-100229: GStreamer H.266 Parser Buffer Overflow

CVE-2026-100229 Overview

CVE-2026-100229 is an out-of-bounds write vulnerability in GStreamer's H.266 codec parser library (libgstcodecparsers). The flaw resides in the Decoding Capability Information (DCI) parsing function, which incorrectly accepts a reserved field value. This acceptance causes the parser to write beyond the bounds of an internal structure [CWE-787]. An attacker can exploit the issue by delivering a crafted H.266 bitstream to a third-party application that invokes the affected library API. No standard GStreamer pipeline element currently reaches the vulnerable code path, which limits real-world exposure.

Critical Impact
A remote attacker can trigger a crash or memory corruption in third-party applications that call the affected libgstcodecparsers DCI parsing API with attacker-controlled H.266 input.

Affected Products

GStreamer libgstcodecparsers H.266 codec parser library
Third-party applications that directly invoke the affected DCI parsing API
Red Hat distributions shipping the vulnerable GStreamer component (refer to vendor advisory for exact builds)

Discovery Timeline

2026-10-14 - CVE-2026-100229 published to the National Vulnerability Database (NVD)
2026-10-14 - Last updated in NVD database

Technical Details for CVE-2026-100229

Vulnerability Analysis

The vulnerability lives in the DCI parser inside libgstcodecparsers, the shared parsing library used by GStreamer codec plugins. H.266 (Versatile Video Coding, VVC) bitstreams include a DCI syntax structure that advertises decoder capability requirements. The parser performs insufficient validation on a reserved field value and treats an out-of-range value as valid. When this occurs, the function writes data past the end of an internal fixed-size structure, producing an out-of-bounds write condition.

The realistic impact is a process crash or targeted memory corruption inside the host application. Because standard GStreamer pipeline elements do not currently invoke the affected DCI code path, the vulnerability only triggers when a third-party application calls the parser API directly on untrusted input. Media players, transcoders, and video processing services that wrap libgstcodecparsers for custom VVC handling are the primary exposure surface.

Root Cause

The parser treats a value that the H.266 specification reserves as invalid as if it were an acceptable count or index. The code then uses that value to drive a write into an internal structure sized for the specification-defined range. The missing bounds check against the reserved value directly produces the out-of-bounds write [CWE-787].

Attack Vector

Exploitation requires an attacker to supply a crafted H.266 bitstream to a vulnerable third-party application. The attack is network-reachable when the application accepts remote media (for example, a streaming client, a server-side transcoder, or a browser-adjacent media stack). No privileges or user interaction beyond opening or processing the media are required. The attacker-controlled bytes influence the write, enabling denial of service and, depending on heap layout, limited memory corruption.

No verified public proof-of-concept code is referenced in the advisory. See the Red Hat CVE-2026-100229 Advisory and the Red Hat Bug Report #2541471 for upstream technical detail.

Detection Methods for CVE-2026-100229

Indicators of Compromise

Unexpected crashes, segmentation faults, or SIGABRT events in processes that link libgstcodecparsers while handling H.266/VVC content
Core dumps whose stack frames reference the DCI parsing routine inside libgstcodecparsers
Inbound media payloads advertising H.266/VVC codec with malformed or reserved DCI field values

Detection Strategies

Inventory applications and services that dynamically load libgstcodecparsers and flag any that call the DCI parsing API on untrusted input
Enable AddressSanitizer or equivalent heap instrumentation in pre-production builds to catch out-of-bounds writes during fuzzing of H.266 inputs
Alert on repeated abnormal termination of media handling processes correlated with ingestion of VVC streams

Monitoring Recommendations

Capture process crash telemetry from endpoints and media processing servers and route it to a central analytics pipeline
Monitor package inventories for installed GStreamer versions and compare against vendor-fixed releases
Log and review third-party application exposure to externally sourced H.266 media, including upload endpoints and streaming ingest

How to Mitigate CVE-2026-100229

Immediate Actions Required

Apply vendor-provided GStreamer updates as soon as patched packages are available for your distribution
Identify third-party applications that call libgstcodecparsers DCI parsing APIs directly and prioritize them for patching
Restrict ingestion of untrusted H.266/VVC bitstreams at network and application boundaries until patches are deployed

Patch Information

At publication, remediation is tracked through distribution advisories. Monitor the Red Hat CVE-2026-100229 Advisory and the associated Red Hat Bug Report #2541471 for fixed package versions, and consult upstream GStreamer release notes for the corresponding commit in libgstcodecparsers.

Workarounds

Disable H.266/VVC codec handling in applications that do not require it
Sandbox media parsing processes with seccomp, namespaces, or equivalent OS isolation to contain memory corruption impact
Validate or reject H.266 bitstreams at an upstream proxy where feasible, dropping streams with malformed DCI structures

bash

# Configuration example: identify processes using the vulnerable library on Linux
lsof 2>/dev/null | grep libgstcodecparsers

# Check installed GStreamer package version (RPM-based systems)
rpm -qa | grep -i gstreamer

# Check installed GStreamer package version (Debian-based systems)
dpkg -l | grep -i gstreamer