CVE-2021-3497 – This vulnerability in GStreamer's Matroska demu... (How to Fix)

Q: What is the severity of CVE-2021-3497?

CVE-2021-3497 has a CVSS score of 7.8 (HIGH). This vulnerability in GStreamer's Matroska demuxer allows attackers to trigger use-after-free conditions by processing specially crafted media files. Successful exploitation could lead to arbitrary code execution or application crashes. Any system using vulnerable GStreamer versions to process untrusted media files is affected.

📋 TL;DR

This vulnerability in GStreamer's Matroska demuxer allows attackers to trigger use-after-free conditions by processing specially crafted media files. Successful exploitation could lead to arbitrary code execution or application crashes. Any system using vulnerable GStreamer versions to process untrusted media files is affected.

💻 Affected Systems

Products:

GStreamer
Applications using GStreamer for media processing

Versions: All versions before 1.18.4

Operating Systems: Linux, Unix-like systems, Any OS with GStreamer

Default Config Vulnerable: ⚠️ Yes

Notes: Vulnerability triggers when processing malformed Matroska (.mkv, .webm) files through the Matroska demuxer.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution with the privileges of the application using GStreamer, potentially leading to full system compromise.

🟠

Likely Case

Application crash (denial of service) when processing malicious media files, potentially disrupting media processing services.

🟢

If Mitigated

Limited to denial of service if memory protections like ASLR are effective, or no impact if untrusted media files are not processed.

🌐 Internet-Facing: MEDIUM - Risk exists for web services that process user-uploaded media files, but requires specific file processing scenarios.

🏢 Internal Only: LOW - Requires local users to process malicious files or specific media processing workflows.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Proof-of-concept exploit code exists in security advisories. Exploitation requires crafting specific malformed Matroska files.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 1.18.4 and later

Vendor Advisory: https://gstreamer.freedesktop.org/security/sa-2021-0002.html

Restart Required: Yes

Instructions:

1. Update GStreamer to version 1.18.4 or later. 2. For Linux distributions, use package manager: 'sudo apt update && sudo apt upgrade gstreamer1.0' (Debian/Ubuntu) or 'sudo yum update gstreamer' (RHEL/CentOS). 3. Restart applications using GStreamer.

🔧 Temporary Workarounds

Disable Matroska file processing

linux

Prevent GStreamer from processing Matroska files by removing or disabling the Matroska demuxer plugin.

sudo mv /usr/lib/gstreamer-1.0/libgstmatroska.so /usr/lib/gstreamer-1.0/libgstmatroska.so.disabled

Input validation

all

Implement file type validation and sanitization before passing media files to GStreamer.

🧯 If You Can't Patch

Implement strict input validation for all media files processed by applications using GStreamer.
Isolate media processing services in containers or VMs with limited privileges and network access.

🔍 How to Verify

Check if Vulnerable:

Check GStreamer version: 'gst-inspect-1.0 --version' and verify if below 1.18.4.

Check Version:

gst-inspect-1.0 --version

Verify Fix Applied:

Confirm version is 1.18.4 or higher: 'gst-inspect-1.0 --version | grep -q "1\.1[89]\|1\.[2-9]" && echo "Patched"'.

📡 Detection & Monitoring

Log Indicators:

Application crashes with segmentation faults in GStreamer components
Error messages related to Matroska demuxing or memory access

Network Indicators:

Unusual media file uploads to web services
Requests for media processing with malformed files

SIEM Query:

source="application_logs" AND ("segmentation fault" OR "SIGSEGV") AND process="*gstreamer*"

📊 Metadata

CVE ID: CVE-2021-3497

CVSS v3 Score: 7.8 (HIGH)

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CWE: CWE-416

Published: April 19, 2021

Last Updated: November 21, 2024

🔗 References

https://bugzilla.redhat.com/show_bug.cgi?id=1945339 Issue Tracking,Patch,Third Party Advisory
https://gstreamer.freedesktop.org/security/sa-2021-0002.html Vendor Advisory
https://lists.debian.org/debian-lts-announce/2021/04/msg00027.html Mailing List,Third Party Advisory
https://security.gentoo.org/glsa/202208-31 Third Party Advisory
https://www.debian.org/security/2021/dsa-4900 Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1945339 Issue Tracking,Patch,Third Party Advisory
https://gstreamer.freedesktop.org/security/sa-2021-0002.html Vendor Advisory
https://lists.debian.org/debian-lts-announce/2021/04/msg00027.html Mailing List,Third Party Advisory
https://security.gentoo.org/glsa/202208-31 Third Party Advisory
https://www.debian.org/security/2021/dsa-4900 Third Party Advisory

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