CVE-2026-19389 Overview
CVE-2026-19389 affects the GStreamer gst-plugins-ugly ASF demuxer (asfdemux) when it parses header objects from crafted ASF, WMV, or WMA files. Multiple integer overflow and underflow conditions in the parser allow attacker-controlled length and size values to bypass bounds checks. The resulting out-of-bounds heap reads can crash the media pipeline, cause denial of service, or leak limited information from adjacent memory. GStreamer is embedded in Linux desktop environments, media players, and application frameworks that automatically process untrusted media, expanding the attack surface to any workflow that opens third-party audio or video files.
Critical Impact
Processing a crafted ASF, WMV, or WMA file with a vulnerable asfdemux build can crash the host application and expose limited process memory to an attacker.
Affected Products
- GStreamer gst-plugins-uglyasfdemux element (versions prior to the fix landed in GStreamer 1.28)
- Linux distributions shipping affected gst-plugins-ugly packages, including Red Hat products tracked under Red Hat CVE-2026-19389
- Applications embedding GStreamer for ASF, WMV, or WMA playback and thumbnailing
Discovery Timeline
- 2026-08-10 - CVE-2026-19389 published to NVD
- 2026-08-10 - Last updated in NVD database
Technical Details for CVE-2026-19389
Vulnerability Analysis
The defect is an integer overflow class weakness [CWE-190] inside asfdemux header object parsing. ASF containers describe internal structures using attacker-supplied 32-bit and 64-bit size fields. The demuxer performs arithmetic on these fields (for example, additions of header lengths plus fixed offsets) before validating them against the remaining buffer size. When the arithmetic wraps past the maximum integer value, the resulting small size passes the length check while the parser still reads far beyond the allocated buffer. Delivery only requires a user to open a malicious file or navigate to a page that autoplays one, matching the network attack vector with user interaction requirement noted in the advisory.
Root Cause
Header object size and length fields are consumed directly from the file and combined arithmetically without saturating or checked-arithmetic helpers. Both overflow (large + large wraps to small) and underflow (subtraction of a header prefix from an attacker-supplied small length) invalidate the bounds check. Subsequent memory reads use the untrusted length verbatim, producing out-of-bounds heap reads inside the demuxer's parsing routines.
Attack Vector
An attacker crafts an ASF, WMV, or WMA file that sets header object lengths to values which overflow during size computation. The file is delivered by email attachment, drive-by download, chat, or media share. When a GStreamer-backed application, thumbnailer, or transcoder opens the file, asfdemux reads outside the header buffer, producing a crash or leaking bytes that follow the buffer on the heap. See the GStreamer Security Advisory SA-2026-0075 and the GitLab Merge Request #12233 for the parsing paths involved.
// No verified public proof-of-concept is available.
// Refer to the upstream merge request for the corrected bounds arithmetic.
Detection Methods for CVE-2026-19389
Indicators of Compromise
- Repeated crashes or SIGSEGV signals from processes linked against libgstasf or invoking gst-launch-1.0 with ASF, WMV, or WMA inputs.
- systemd-coredump or abrt entries referencing asfdemux frames in the stack trace.
- Inbound ASF, WMV, or WMA files with malformed header object sizes flagged by mail or web gateways.
Detection Strategies
- Inventory hosts running gst-plugins-ugly below the fixed release using package managers and file integrity data.
- Alert on media player, thumbnailer, or transcoder processes that terminate abnormally while handling ASF-family containers.
- Correlate media file downloads with subsequent process crashes on the same endpoint to surface exploitation attempts.
Monitoring Recommendations
- Ingest application crash telemetry and core dump metadata into the SIEM for retroactive hunting on asfdemux frames.
- Monitor content delivery paths (email, chat, web proxies) for ASF, WMV, and WMA attachments and record hashes for reputation checks.
- Track EPSS movement for CVE-2026-19389 to reprioritize patching if exploitation likelihood increases.
How to Mitigate CVE-2026-19389
Immediate Actions Required
- Upgrade GStreamer and gst-plugins-ugly to the patched release referenced in the GStreamer 1.28 release announcement.
- Apply vendor security updates from downstream distributions, tracked in the Red Hat Bug Report #2513016.
- Block or quarantine unsolicited ASF, WMV, and WMA files at mail and web gateways until patching completes.
Patch Information
The fix lands upstream via GitLab Merge Request #12233 and ships in GStreamer 1.28. Distribution-specific packages are tracked in the Red Hat advisory for CVE-2026-19389. Rebuild or reinstall any application bundling a private copy of gst-plugins-ugly.
Workarounds
- Disable or remove the asfdemux element where ASF, WMV, and WMA playback is not required.
- Configure GStreamer application rank so alternative demuxers or sandboxed converters handle untrusted media.
- Restrict automatic media preview and thumbnailing on file servers and shared workstations until patches are deployed.
# Confirm installed gst-plugins-ugly version and remove asfdemux where unneeded
rpm -q gstreamer1-plugins-ugly-free || dpkg -l | grep gst-plugins-ugly
gst-inspect-1.0 asfdemux | head -n 5
# Example: lower asfdemux rank so it is not auto-selected for untrusted input
export GST_PLUGIN_FEATURE_RANK=asfdemux:NONE
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
