CVE-2026-90576: GPAC MP4Box Null Pointer Dereference Flaw

CVE-2026-90576 Overview

CVE-2026-90576 is a null pointer dereference vulnerability [CWE-404] in GPAC, an open-source multimedia framework, up to commit f1219cde. The flaw resides in the gf_node_list_add_child function within scenegraph/base_scenegraph.c, a component used by the MP4Box utility. Processing a crafted input file triggers a null pointer dereference, resulting in a segmentation fault and process termination. The issue requires local access and low privileges to trigger, and the exploit has been disclosed publicly. Upgrading to GPAC release abi-16.23 remediates the issue via commit 49dee5cad329cfed310c1682703df7daa47df31a.

Critical Impact
A local attacker with low privileges can crash the MP4Box process by supplying a malformed media file, causing a denial of service against workflows that parse untrusted multimedia content.

Affected Products

GPAC multimedia framework up to commit f1219cde
MP4Box command-line utility bundled with GPAC
Any downstream tools that link against the affected scenegraph/base_scenegraph.c code path

Discovery Timeline

2026-09-13 - CVE CVE-2026-90576 published to the National Vulnerability Database (NVD)
2026-09-14 - Last updated in NVD database

Technical Details for CVE-2026-90576

Vulnerability Analysis

The vulnerability is a null pointer dereference [CWE-404] inside gf_node_list_add_child, a helper that appends a scene-graph node to a linked list of children. When MP4Box processes a malformed BIFS scene or multimedia container, the code path reaches the helper without a valid node pointer initialized. Dereferencing that null pointer generates a SIGSEGV and terminates the process.

The impact is limited to availability. The confidentiality and integrity of processed data are not affected, and the flaw does not enable code execution or privilege escalation. Exposure is highest for automated pipelines, transcoders, and media ingestion services that invoke MP4Box on files supplied by users or external systems. The vendor addressed the issue in release abi-16.23.

Root Cause

The root cause is missing validation of node pointers before insertion into scene-graph child lists. The patched code introduces a wrapper (gf_sg_command_set_node) that centralizes node assignment and register operations, along with additional memory-tracking fixes in the AV1 reframer. These changes ensure that node references and packet references are released or validated during fuzz-generated edge cases.

Attack Vector

Exploitation requires local access and the ability to supply an attacker-controlled file to MP4Box. A remote attacker cannot trigger the flaw directly over a network, but a media-processing service that ingests external files effectively converts the local vector into a remote denial-of-service condition. No authentication beyond the ability to run MP4Box on the target file is required.

// Patch excerpt: src/bifs/memory_decoder.c
static void BM_SetCommandNode(GF_Command *com, GF_Node *node)
{
-	com->node = node;
+	gf_sg_command_set_node(com, node);
 	gf_node_register(node, NULL);
}

Source: GitHub Commit 49dee5c

// Patch excerpt: src/filters/reframe_av1.c
	GF_AV1DmxCtx *ctx = gf_filter_get_udta(filter);
	if (ctx->bs) gf_bs_del(ctx->bs);
	if (ctx->indexes) gf_free(ctx->indexes);
+	if (ctx->src_pck) gf_filter_pck_unref(ctx->src_pck);

	gf_av1_reset_state(&ctx->state, GF_TRUE);
	if (ctx->state.config) gf_odf_av1_cfg_del(ctx->state.config);

Source: GitHub Commit 49dee5c

Detection Methods for CVE-2026-90576

Indicators of Compromise

Repeated segmentation faults (SIGSEGV) originating from the MP4Box binary in system or crash logs.
Core dumps referencing the gf_node_list_add_child symbol or scenegraph/base_scenegraph.c.
Unexpected termination of media-processing pipelines shortly after ingesting user-supplied multimedia files.

Detection Strategies

Inventory hosts running GPAC and compare installed versions against the patched abi-16.23 release.
Monitor process-exit telemetry for MP4Box crashes correlated with recently ingested input files.
Retain crash artifacts and malformed input samples for triage against the published proof-of-concept in the Rick9 CVE Summit Analysis.

Monitoring Recommendations

Alert on abnormal termination rates for media-processing services that wrap MP4Box.
Forward MP4Box stderr and system crash logs to a central logging pipeline for review.
Track file-integrity events on the GPAC binary and its shared libraries to detect unpatched installations.

How to Mitigate CVE-2026-90576

Immediate Actions Required

Upgrade GPAC to release abi-16.23 or later on all systems that execute MP4Box.
Restrict which user accounts can invoke MP4Box and limit access to media-ingestion directories.
Validate and sandbox untrusted media files before processing them with GPAC utilities.

Patch Information

The fix is committed as 49dee5cad329cfed310c1682703df7daa47df31a and shipped in the GitHub Release abi-16.23. Additional context is available in GitHub Issue #3815 and the VulDB CVE-2026-90576 entry. Rebuild any downstream packages that statically link GPAC libraries after applying the update.

Workarounds

Run MP4Box inside a container or sandbox with resource limits so that a crash does not disrupt the parent workflow.
Reject or pre-filter malformed BIFS and scene-graph inputs at the ingestion boundary using a schema check.
Where upgrade is not immediately feasible, disable automated MP4Box invocation on attacker-controlled files until the patch is applied.

bash

# Verify installed GPAC version and upgrade to the patched release
MP4Box -version
git clone https://github.com/gpac/gpac.git
cd gpac
git checkout abi-16.23
./configure && make && sudo make install
MP4Box -version   # confirm abi-16.23 or later