CVE-2026-52718: GStreamer AV1 Parser DoS Vulnerability

CVE-2026-52718 Overview

CVE-2026-52718 is a denial of service vulnerability in GStreamer's AV1 codec parser, shipped as part of the gst-plugins-bad package. The flaw resides in the gst_av1_parser_parse_tile_list_obu() function, which passes a byte count to a bit-reader API that expects a bit count. This unit mismatch desynchronizes the parser state and leads to an assertion abort. A remote attacker can craft a malicious AV1 media file that, when opened by a victim, triggers the assertion and crashes the host application. The issue is categorized under [CWE-617] Reachable Assertion.

Critical Impact
A specially crafted AV1 file can crash any application that links GStreamer's AV1 parser, including media players, browsers, and thumbnailers that automatically process untrusted media.

Affected Products

GStreamer gst-plugins-bad AV1 codec parser
Applications and frameworks embedding GStreamer for AV1 media playback
Linux distributions packaging vulnerable versions of gst-plugins-bad

Discovery Timeline

2026-06-15 - CVE-2026-52718 published to the National Vulnerability Database
2026-06-17 - Last updated in the NVD database

Technical Details for CVE-2026-52718

Vulnerability Analysis

The defect lives in gst_av1_parser_parse_tile_list_obu(), the routine responsible for parsing AV1 Tile List Open Bitstream Units (OBUs). AV1 bitstreams are read using a bit-granular reader so that variable-length fields can be extracted from non-byte-aligned positions. The parser supplies a byte-denominated length value to a reader API whose contract requires the count in bits. As a result, the reader advances by a value eight times smaller than intended, leaving the parser at an inconsistent bitstream offset for subsequent OBU processing.

Downstream code paths then encounter values that violate internal invariants. When these invariants are checked by an assertion, the assertion fails and the host process aborts. The vulnerability requires user interaction because the victim must open or preview the crafted file. Because GStreamer is widely embedded, the attack surface includes media players, file managers performing thumbnail generation, and browser-based media pipelines on Linux desktops.

Root Cause

The root cause is a unit confusion bug between byte-counted and bit-counted APIs inside the AV1 OBU parser. The mismatched length argument causes parser desynchronization, after which a runtime assertion in the bit reader or a subsequent OBU handler aborts the process.

Attack Vector

An attacker hosts or delivers a malicious AV1 file, for example through a web page, email attachment, instant messaging, or a shared file location. When a user opens the file with an application backed by GStreamer, the AV1 parser is invoked, the assertion fires, and the application terminates. Repeated delivery can be used to deny access to media services or to disrupt automated media-processing workflows.

No verified public proof-of-concept code is available. Refer to the GStreamer Work Item #5103 and the Red Hat CVE-2026-52718 Advisory for upstream technical context.

Detection Methods for CVE-2026-52718

Indicators of Compromise

Unexpected SIGABRT terminations of media-handling processes such as gst-launch-1.0, totem, rhythmbox, or browser media subprocesses after opening AV1 content.
Core dumps referencing gst_av1_parser_parse_tile_list_obu or gst_bit_reader frames in the backtrace.
Inbound AV1 (.ivf, .mkv, .mp4, .webm) files from untrusted sources that consistently crash media previewers or thumbnailers.

Detection Strategies

Monitor application crash telemetry and coredumpctl output for assertion aborts in GStreamer AV1 code paths.
Inspect AV1 streams at the gateway for malformed Tile List OBUs using format validators where AV1 traffic is expected.
Correlate file-open events with subsequent process termination to surface targeted DoS attempts against specific users.

Monitoring Recommendations

Forward syslog, journald, and ABRT events to a central log platform and alert on repeated GStreamer crashes from the same user or media source.
Track package versions of gst-plugins-bad across the fleet to identify hosts still running vulnerable builds.
Audit endpoints that automatically render media previews, as these process untrusted input without explicit user action beyond directory navigation.

How to Mitigate CVE-2026-52718

Immediate Actions Required

Apply distribution updates for gst-plugins-bad as soon as patched packages are published by your vendor.
Restrict opening AV1 files from untrusted sources until patches are deployed.
Disable automatic media thumbnailing in file managers on multi-user and kiosk systems to reduce exposure to drive-by parsing.

Patch Information

A fix is tracked upstream in GStreamer Work Item #5103. Vendor coordination details are available in the Red Hat CVE-2026-52718 Advisory and the corresponding Red Hat Bug Report #2486328. Update to the patched gst-plugins-bad version provided by your Linux distribution once available.

Workarounds

Remove or unregister the AV1 parser plugin from GStreamer where AV1 playback is not required.
Use GST_PLUGIN_FEATURE_RANK environment variables or registry edits to demote the AV1 parser so that AV1 content fails closed rather than reaching the vulnerable code path.
Block AV1 media at email and web gateways for high-risk user populations until patching is complete.

bash

# Configuration example: disable the AV1 parser feature in GStreamer
export GST_PLUGIN_FEATURE_RANK=av1parse:NONE

# Verify the plugin rank has been lowered
gst-inspect-1.0 av1parse | grep -i rank